Quiz #5- Senses and Endocrine system Flashcards
(154 cards)
1
Q
what is The somatosensory system
A
The somatosensory system is responsible for our sense of touch, pressure, temperature, and body position.
2
Q
what does the somatosensory system consist of
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It includes receptors in the skin, muscles, joints, and other tissues that detect various stimuli and send signals to the brain.
3
Q
what are the nerve endings in somatosensory system
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It includes free nerve endings that detect pain, temperature, and some touch sensations, as well as encapsulated nerve endings that detect pressure, vibration, and other touch sensations.
4
Q
different types of receptors in the somatosensory system
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There are different types of receptors, like
mechanoreceptors that detect mechanical stimuli,
thermoreceptors that detect temperature changes, and
nociceptors that detect painful stimuli.
5
Q
Mechanoreceptors
A
Mechanoreceptors are sensory receptors that detect mechanical stimuli, such as touch, pressure, vibration, and movement. They are found in the skin, muscles, joints, and other tissues throughout the body.
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Q
different types of mechanoreceptors
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Meissner’s corpuscles - Detect light touch and flutter
Pacinian corpuscles - Detect deep pressure and vibration
Ruffini endings - Detect skin stretch and joint position
Merkel’s discs - Detect sustained pressure and texture
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Q
Meissner’s corpuscles
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- Detect light touch and flutter
8
Q
Pacinian corpuscles
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Detect deep pressure and vibration
9
Q
Ruffini endings
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Ruffini endings - Detect skin stretch and joint position
10
Q
Merkel’s discs
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Detect sustained pressure and texture
11
Q
example of somatosensory system
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For example, when you lightly touch a smooth surface, the Meissner’s corpuscles in your fingertips detect the gentle pressure and send signals to your brain, allowing you to perceive the softness of the material. Pretty cool, right?
12
Q
Thermoreceptors
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Thermoreceptors are a type of sensory receptor that detect changes in temperature. They are found in the skin and other tissues throughout the body.
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Q
two main types of Thermoreceptors
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Cold receptors - These are larger, myelinated nerve fibers that are located in the upper layers of the skin. They respond to decreases in temperature and send signals to the brain that we interpret as a “cold” sensation.
Warm receptors - These are smaller, unmyelinated nerve fibers that are located deeper in the dermis layer of the skin. They respond to increases in temperature and send signals that we perceive as “warmth.”
14
Q
how do thermoreceptors work?
A
The thermoreceptors work by converting the thermal energy (heat or cold) into electrical signals that travel along the somatosensory pathways to the brain. In the brain, these signals are processed and interpreted, allowing us to feel and distinguish between hot, cold, and neutral temperatures.
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Q
Cold receptors
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These are larger, myelinated nerve fibers that are located in the upper layers of the skin. They respond to decreases in temperature and send signals to the brain that we interpret as a “cold” sensation.
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Q
Warm receptors
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These are smaller, unmyelinated nerve fibers that are located deeper in the dermis layer of the skin. They respond to increases in temperature and send signals that we perceive as “warmth.”
17
Q
main types of proprioceptors:
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Muscle spindles - Located within the muscle fibers, these detect changes in muscle length and tension, allowing us to sense the position and movement of our limbs.
Golgi tendon organs - Found at the junction of muscles and tendons, these detect changes in muscle force and tension, providing information about the amount of effort being exerted.
Joint receptors - Located in the joint capsules and ligaments, these detect the position and movement of our joints.
18
Q
Muscle spindles
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Located within the muscle fibers, these detect changes in muscle length and tension, allowing us to sense the position and movement of our limbs
19
Q
Golgi tendon organs
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Found at the junction of muscles and tendons, these detect changes in muscle force and tension, providing information about the amount of effort being exerted.
20
Q
Proprioceptors
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Proprioceptors are sensory receptors that detect the position and movement of our body parts. They are found in our muscles, tendons, joints, and other tissues.
21
Q
Joint receptors
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Joint receptors - Located in the joint capsules and ligaments, these detect the position and movement of our joints.
22
Q
how do proprioceptors work?
A
These proprioceptors convert mechanical stimuli, like muscle stretch or joint rotation, into electrical signals that travel through the somatosensory pathways to the brain. In the brain, these signals are processed and integrated, allowing us to have a constant awareness of our body’s position and movements.
23
Q
main types of nociceptors:
A
Mechanical nociceptors - These detect intense mechanical forces, like a sharp object piercing the skin.
Thermal nociceptors - These detect extreme temperatures, both hot and cold, that could potentially damage tissue.
These can respond to multiple types of stimuli, including mechanical, thermal, and chemical.
24
Q
Nociceptors
A
Nociceptors are a type of sensory receptor that respond to potentially damaging or painful stimuli. They are found in the skin, muscles, joints, and internal organs throughout the body.
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Mechanical nociceptors
These detect intense mechanical forces, like a sharp object piercing the skin.
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Thermal nociceptors
These detect extreme temperatures, both hot and cold, that could potentially damage tissue.
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Polymodal nociceptors
These can respond to multiple types of stimuli, including mechanical, thermal, and chemical.
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how do nociceptors work?
When these nociceptors are activated by a harmful or potentially harmful stimulus, they generate electrical signals that travel through the somatosensory pathways to the spinal cord and brain. In the brain, these signals are interpreted as the sensation of pain.
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Baroreceptors
Baroreceptors are a type of mechanoreceptor that detect changes in blood pressure and blood volume. They are found in the walls of blood vessels, particularly in the carotid arteries and aorta.
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signals and triggers a response to help regulate blood pressure.
Decreasing the activity of the sympathetic nervous system, which lowers heart rate and blood vessel constriction
Increasing the activity of the parasympathetic nervous system, which further slows the heart rate
Stimulating the kidneys to excrete more water and sodium, reducing blood volume
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what does the baroreceptor reflex help with
This baroreceptor reflex helps maintain a stable blood pressure and prevent dangerous spikes or drops in blood pressure.
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Photoreceptors
Photoreceptors are specialized sensory cells found in the retina of the eye. They are responsible for converting light energy into electrical signals that the brain can interpret as vision.
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two main types of photoreceptors:
Rods - These are more numerous and highly sensitive to light, allowing us to see in low-light conditions. Rods are responsible for our black-and-white, peripheral vision.
Cones - These are less numerous but more specialized for color vision. There are three types of cones, each sensitive to different wavelengths of light (red, green, or blue). Cones allow us to perceive a wide range of colors.
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Rods
These are more numerous and highly sensitive to light, allowing us to see in low-light conditions. Rods are responsible for our black-and-white, peripheral vision.
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Cones
These are less numerous but more specialized for color vision. There are three types of cones, each sensitive to different wavelengths of light (red, green, or blue). Cones allow us to perceive a wide range of colors.
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how do photoreceptors work?
When light enters the eye and reaches the retina, it strikes the photoreceptors. This causes changes in the photoreceptor cells, generating electrical signals that are then transmitted through the optic nerve to the brain.
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perception
Perception is the conscious awareness and interpretation of the sensations we experience through our senses. It's not just about detecting the stimulus, but about how our brain organizes and gives meaning to that information.
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process of perception
Sensation - Our sensory receptors (like photoreceptors, mechanoreceptors, etc.) detect various stimuli in the environment and convert them into electrical signals.
Transduction - These electrical signals are then transmitted through the nervous system to the brain.
Organization - In the brain, the signals are organized and integrated with our past experiences and knowledge.
Interpretation - Finally, the brain interprets the organized sensory information, allowing us to consciously perceive and make sense of the world around us.
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Adaptation
is a decrease in the sensitivity of a sensory receptor to a constant or repeated stimulus. This allows our senses to adjust and prevent us from being overwhelmed by unchanging sensations.
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different types of adaption
Sensory adaptation - This is when a sensory receptor, like a photoreceptor or mechanoreceptor, becomes less responsive to a constant stimulus over time. For example, you stop noticing the feeling of your clothes on your skin after a while.
Neural adaptation - This is when the neurons in the sensory pathways become less responsive to a repeated stimulus. This helps prevent sensory overload in the brain.
Perceptual adaptation - This is when our brain adjusts its interpretation of a sensory input over time. For example, when you get a new pair of glasses, it takes a little while for your brain to adapt to the new visual input.
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Projection
Projection is the process by which our brain determines the location of a sensory stimulus in the external world. It allows us to know where a sensation is originating from, even if we can't see the source directly.
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projection examples
Touch - When you touch something, the somatosensory receptors in your skin send signals to your brain. Your brain can then project the sensation to the exact location on your body where the touch occurred.
Hearing - The way sound waves reach your two ears at slightly different times and volumes allows your brain to project the location of the sound source in space.
Vision - The inverted image that is focused on your retina is "flipped" by your brain, allowing you to perceive the world in its proper orientation.
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Referred pain
Referred pain occurs when we feel pain in an area of the body that is not the actual site of the injury or problem. This happens because of the way our sensory nerves are organized and connected in the body.
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how does referred pain work
Certain internal organs, like the heart or gallbladder, share nerve connections with the skin and muscles of the body wall.
When there is a problem with an internal organ, the pain signals can get "referred" or projected to the related area of the body wall.
For example, pain from a heart attack is often felt in the left arm or shoulder, even though the heart is the source of the problem.
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why referred pain happens
This happens because the brain has difficulty precisely localizing the origin of the pain signals when they are coming from internal organs. Instead, the brain interprets the pain as coming from the area of the body wall that shares the same nerve connections.
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Cornea
Cornea - The clear, curved front part of the eye that refracts (bends) light as it enters the eye.
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Pupil
The opening in the center of the iris that controls the amount of light entering the eye.
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Iris
The colored part of the eye that contains muscles that dilate and constrict the pupil.
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Lens
The transparent, flexible structure behind the iris that further focuses light onto the retina.
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Retina
Retina - The light-sensitive layer at the back of the eye that contains photoreceptors (rods and cones) to convert light into electrical signals.
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Optic Nerve
Transmits the electrical signals from the retina to the brain, where they are interpreted as vision.
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Sclera
The white, protective outer layer of the eye
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Vitreous Humor
The clear, jelly-like substance that fills the space between the lens and the retina, helping to maintain the shape of the eye.
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Choroid
The layer between the sclera and retina that provides blood supply to the eye.
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Eyelids
These protect the eye and help distribute tears across the surface of the eye.
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Eyelashes
These act as a first line of defense, trapping dust and debris before it can enter the eye.
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Eyebrows -
These help shield the eyes from sweat and direct light.
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Lacrimal System
This includes the tear glands, tear ducts, and tear drainage system. It produces, distributes, and drains the tears that lubricate and protect the eye.
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Extrinsic Eye Muscles -
These six muscles (superior, inferior, lateral, and medial rectus; superior and inferior oblique) control the movement and positioning of the eyeball.
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Conjunctiva
This is the thin, transparent membrane that lines the inner eyelids and covers the front of the sclera.
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the pathway for light as it enters the eye and reaches the optic nerve
1. Cornea - Light waves first enter the eye through the clear, curved cornea. The cornea refracts (bends) the light, helping to focus it.
2. Pupil - The light then passes through the pupil, the opening in the center of the iris. The size of the pupil can change to control the amount of light entering the eye.
3. Lens - Next, the light travels through the flexible lens, which further focuses the light rays.
4. Vitreous Humor - The light then passes through the vitreous humor, the clear, jelly-like substance that fills the space between the lens and the retina.
5. Retina - The focused light finally reaches the retina, the light-sensitive layer at the back of the eye. The retina contains photoreceptor cells (rods and cones) that convert the light energy into electrical signals.
6. Optic Nerve - These electrical signals are then transmitted through the optic nerve to the brain, where they are interpreted as visual images.
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cranial nerve associated with vision
Optic Nerve (Cranial Nerve II) - Transmits visual information from the retina to the brain.
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cranial nerve associated with hearing and equilibrium
Vestibulocochlear Nerve (Cranial Nerve VIII) - Carries sensory information from the inner ear, including the cochlea (hearing) and vestibular apparatus (balance and equilibrium).
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cranial nerve associated with Gustatory (Taste) Pathway:
Facial Nerve (Cranial Nerve VII) - Innervates taste buds on the anterior two-thirds of the tongue.
Glossopharyngeal Nerve (Cranial Nerve IX) - Innervates taste buds on the posterior one-third of the tongue.
Vagus Nerve (Cranial Nerve X) - Innervates taste buds on the palate, pharynx, and epiglottis.
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parts of the outer ear
Auricle (Pinna) - The visible, outer part of the ear that collects sound waves and channels them into the ear canal.
External Auditory Canal - The tube-like structure that directs the sound waves toward the eardrum.
Tympanic Membrane (Eardrum) - Vibrates when sound waves strike it, transmitting the vibrations to the middle ear.
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Auricle (Pinna)
The visible, outer part of the ear that collects sound waves and channels them into the ear canal. (part of the outer ear)
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External Auditory Canal
The tube-like structure that directs the sound waves toward the eardrum.
(part of the outer ear)
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Tympanic Membrane (Eardrum)
Vibrates when sound waves strike it, transmitting the vibrations to the middle ear. (part of pouter ear)
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parts of the middle ear
Auditory Ossicles - The three tiny bones (malleus, incus, and stapes) that transmit the vibrations from the eardrum to the oval window of the inner ear.
Eustachian Tube - Connects the middle ear to the back of the throat, allowing air pressure to be equalized on both sides of the eardrum.
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Eustachian Tube
Connects the middle ear to the back of the throat, allowing air pressure to be equalized on both sides of the eardrum. (part of the middle ear)
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Eustachian Tube
Connects the middle ear to the back of the throat, allowing air pressure to be equalized on both sides of the eardrum.
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parts of the inner ear
Cochlea - Contains the organ of Corti, which has hair cells that convert the vibrations into electrical signals for the brain to interpret as sound.
Vestibular System - Includes the utricle, saccule, and semicircular canals, which detect head and body movements and help maintain balance and equilibrium.
Vestibulocochlear Nerve (Cranial Nerve VIII) - Transmits the electrical signals from the inner ear to the brain.
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pathway for sound vibrations including all relevant structures
1. Auricle (Pinna) - Sound waves are collected and funneled into the external auditory canal by the outer ear.
2. External Auditory Canal - The sound waves travel through the canal and strike the tympanic membrane (eardrum).
3. Tympanic Membrane - The vibrations of the eardrum are then transmitted to the auditory ossicles (malleus, incus, and stapes) in the middle ear.
4. Auditory Ossicles - The vibrations of the ossicles are amplified and passed on to the oval window, which is the entrance to the inner ear.
5. Oval Window - The vibrations of the oval window create pressure waves in the fluid-filled cochlea of the inner ear.
6. Cochlea - Inside the cochlea, the pressure waves bend the hair cells of the organ of Corti, which converts the mechanical vibrations into electrical signals.
7. Vestibulocochlear Nerve (Cranial Nerve VIII) - These electrical signals are then transmitted through the vestibulocochlear nerve to the brain, where they are interpreted as sound.
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Vestibulocochlear Nerve (Cranial Nerve VIII)
Transmits the electrical signals from the inner ear to the brain. (part of the inner ear)
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Cochlea
Contains the organ of Corti, which has hair cells that convert the vibrations into electrical signals for the brain to interpret as sound.
(part of inner ear)
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Static Equilibrium:
Static equilibrium is the sense of body orientation relative to the pull of gravity when the head and body are still.
The receptors for static equilibrium are located in the utricle and saccule of the inner ear.
These receptors contain hair cells that are stimulated by the movement of otoliths (calcium carbonate crystals) in response to gravity.
This allows us to sense the position of our head and body when we are not moving.
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Vestibular System
Includes the utricle, saccule, and semicircular canals, which detect head and body movements and help maintain balance and equilibrium. (part of inner ear)
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Dynamic equilibrium
Dynamic equilibrium is the sense of balance and movement in response to rotational acceleration and deceleration.
The receptors for dynamic equilibrium are located in the semicircular canals of the inner ear.
The semicircular canals contain hair cells that are stimulated by the movement of fluid within the canals as the head rotates.
This allows us to detect and respond to changes in the position and movement of our head and body.
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difference between dynamic and static equilibrium
Static equilibrium uses the utricle and saccule to detect orientation relative to gravity.
Dynamic equilibrium uses the semicircular canals to detect rotational movements and changes in acceleration.
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The Gustatory Pathway:
Taste receptors in the taste buds on the tongue, palate, pharynx, and epiglottis detect taste stimuli.
These receptors send signals through the facial (VII), glossopharyngeal (IX), and vagus (X) cranial nerves.
The signals travel to the medulla oblongata, then the thalamus, and finally reach the primary gustatory area in the parietal lobe of the cerebral cortex.
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The 5 Primary Tastes:
Sour
Sweet
Bitter
Salty
Umami (savory/meaty)
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Location of Taste Buds:
The majority of taste buds are located on the tongue, especially on the vallate and fungiform papillae.
There are also some taste buds on the roof of the mouth, the pharynx, and the epiglottis.
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Emotional Response to Food:
Emotional and behavioral responses to taste/food involve the limbic system.
areas of the brain associate taste and food with memories, emotions, and motivations, influencing our likes, dislikes, and cravings.
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parts of the brain responsible for conscious awareness of taste
Conscious taste perception occurs in the primary gustatory area of the parietal lobe.
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Appetite and Hunger Regulation:
Appetite and hunger regulation is primarily controlled by the hypothalamus.
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Lipid-Soluble Hormones:
Lipid -soluble hormones, like steroid hormones and thyroid hormones, are able to easily pass through the cell membrane.
Once inside the target cell, the hormone binds to a specific receptor protein in the cytoplasm or nucleus.
This hormone-receptor complex then binds to specific DNA sequences, called hormone response elements, and alters gene expression.
This changes the activity of the target cell by affecting the synthesis of specific proteins.
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examples of lipid soluble hormones
Examples include estrogen, testosterone, and thyroid hormones (T3 and T4).
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Water-Soluble Hormones:
Water-soluble hormones, like peptide hormones and modified amino acid hormones, cannot easily pass through the cell membrane.
Instead, they bind to receptors on the target cell's surface, activating a second messenger system inside the cell.
This second messenger, like cyclic AMP (cAMP), then triggers a cascade of intracellular reactions that alter the cell's activities.
Water-soluble hormones have a more rapid, short-term effect compared to lipid-soluble hormones.
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examples of water-soluble hormones
Examples include insulin, growth hormone, and antidiuretic hormone (ADH).
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key difference between lipid soluble and water soluble hormones
The key difference is that lipid-soluble hormones can directly enter the target cell and affect gene expression, while water-soluble hormones work through cell surface receptors and second messenger systems. Both mechanisms allow hormones to elicit specific responses in their target cell
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the difference between positive and negative feedback
negative feedback keeps things stable, while positive feedback allows certain processes to rapidly escalate
negative are more common
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Endocrine System Responses:
Uses chemical messengers called hormones released into the bloodstream
Effects are widespread and longer-term, acting over seconds to days
Hormones can target cells throughout the body, even distant from the gland
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Nervous System Responses:
Uses electrical impulses (neurotransmitters) to rapidly transmit signals
Effects are localized and short-term, acting within milliseconds
Targets specific muscle, gland, or other cells near the site of release
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key differences between nervous and endocrine responses
The nervous system is faster and more precise, while the endocrine system is slower but has broader, more global effects.
Nervous system signals are electrical, while endocrine system signals are chemical.
Nervous system acts locally, endocrine system acts systemically.
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the brain structure that controls the pituitary gland
the hypothalamus monitors various conditions in the body and sends signals to the pituitary gland to secrete the appropriate hormones in response. This allows the endocrine system to maintain homeostasis and regulate important bodily functions.
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hGh
Human growth hormone
Source: The anterior pituitary gland
Target Cells: Liver, muscle, bone, and other tissues
Functions:
Stimulates the liver to synthesize and secrete insulin-like growth factors (IGFs)
IGFs then promote growth and reproduction of body cells
Increases protein synthesis
Enhances tissue repair
Speeds up the breakdown of triglycerides and increases blood glucose levels
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PRL
Name: Prolactin (PRL)
Source: Anterior pituitary gland
Target Cells: Mammary glands
Functions:
Initiates and maintains milk production (lactation) in the mammary glands following childbirth
Helps prepare the mammary glands for milk production during pregnancy
Its effects in males are less well understood, but it may play a role in sexual function
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TSH
Name: Thyroid-Stimulating Hormone (TSH)
Source: Anterior pituitary gland
Target Cells: Thyroid gland
Functions:
Stimulates the thyroid gland to synthesize and secrete the thyroid hormones thyroxine (T4) and triiodothyronine (T3)
Helps regulate metabolism, growth, and development in the body
Secretion of TSH is controlled by thyroid-releasing hormone (TRH) from the hypothalamus
As blood levels of T3 and T4 increase, secretion of TSH decreases (negative feedback)
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FSH
Name: Follicle-Stimulating Hormone (FSH)
Source: Anterior pituitary gland
Target Cells:
In females: Ovaries
In males: Testes
Functions:
In females, FSH initiates the development of ovarian follicles and stimulates the secretion of estrogens by the ovaries
In males, FSH stimulates the testes to produce sperm
FSH, along with luteinizing hormone (LH), are known as the "gonadotropins" as they affect the male and female gonads (testes and ovaries)
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LH
Name: Luteinizing Hormone (LH)
Source: Anterior pituitary gland
Target Cells:
In females: Ovaries
In males: Testes
Functions:
In females, LH stimulates the secretion of estrogens and progesterone, triggers ovulation, and helps form the corpus luteum
In males, LH stimulates the testes to produce testosterone
Along with FSH, LH is one of the two "gonadotropins" that regulate the function of the male and female gonads (testes and ovaries).
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ACTH
Name: Adrenocorticotropic Hormone (ACTH)
Source: Anterior pituitary gland
Target Cells: Adrenal cortex
Functions:
Stimulates the adrenal cortex to secrete glucocorticoids, primarily cortisol
Cortisol helps regulate metabolism, immune function, and the body's stress response
ACTH secretion is increased in response to stress, which then leads to increased cortisol production
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MSH
Name: Melanocyte-Stimulating Hormone (MSH)
Source: Anterior pituitary gland
Target Cells: Melanocytes (pigment-producing cells)
Functions:
The exact role of MSH in humans is not fully understood
It may influence brain activity and mood
When present in excess, MSH can cause darkening of the skin (hyperpigmentation)
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Oxytocin
Source: Hypothalamus (produced) and Posterior Pituitary (stored and released)
Target Cells:
Uterus
Mammary glands
Functions:
Stimulates contraction of the smooth muscle cells in the uterus during childbirth, helping to facilitate labor and delivery
Stimulates the milk ejection reflex, causing the release of milk from the mammary glands during breastfeeding
Plays a role in social bonding and trust
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ADH
Name: Antidiuretic Hormone (ADH) or Vasopressin
Source: Hypothalamus (produced) and Posterior Pituitary (stored and released)
Target Cells: Kidneys
Functions:
Increases water reabsorption by the kidneys, leading to decreased urine output
Helps maintain proper fluid balance and blood pressure in the body
Secretion of ADH is controlled by the hypothalamus based on factors like blood osmolarity and blood volume
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T4/T3
Names:
Thyroxine (T4)
Triiodothyronine (T3)
Source: Thyroid gland
Target Cells: Most cells in the body
Functions:
Regulate metabolism, growth, and development
Increase the rate at which cells release energy from carbohydrates and fats
Enhance protein synthesis
Stimulate the breakdown and mobilization of lipids
T4 and T3 are the two main hormones produced by the thyroid gland. T4 is the more abundant form, while T3 is the more potent and active form.
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PTH
Name: Parathyroid Hormone (PTH)
Source: Parathyroid glands
Target Cells: Bone, kidneys, intestines
Functions:
Increases blood calcium levels
Stimulates bone resorption, releasing calcium from bone into the bloodstream
Increases calcium reabsorption in the kidneys, preventing its excretion
Increases calcium absorption from the intestines
PTH is the main regulator of blood calcium levels in the body. It works to counteract decreases in blood calcium by mobilizing calcium from the bones, kidneys, and intestines.
PTH secretion is controlled by a negative feedback loop involving blood calcium concentrations. When calcium levels drop, PTH is released to restore normal levels.
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calcitonin
Name: Calcitonin
Source: Parafollicular (C) cells of the thyroid gland
Target Cells: Bone, kidneys, intestines
Functions:
Helps lower blood calcium levels
Stimulates the storage of calcium in bones
Increases the rate of calcium excretion in the urine
Opposes the effects of parathyroid hormone (PTH), which increases blood calcium
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glucagon
Name: Glucagon
Source: Alpha cells of the pancreatic islets
Target Cells: Liver
Functions:
Increases blood glucose levels
Stimulates the liver to break down glycogen into glucose (glycogenolysis)
Stimulates the liver to convert non-carbohydrates (like amino acids and fats) into glucose (gluconeogenesis)
Glucagon is the counterpart to insulin, which decreases blood glucose levels. Together, insulin and glucagon work to maintain a relatively stable blood glucose concentration.
The release of glucagon is controlled by a negative feedback mechanism involving low blood glucose levels (hypoglycemia). When blood glucose drops, glucagon is secreted to raise it back up.
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insulin
Name: Insulin
Source: Beta cells of the pancreatic islets
Target Cells: Most cells in the body
Functions:
Decreases blood glucose levels
Stimulates the transport of glucose into cells, especially muscle and adipose (fat) cells
Promotes the storage of glucose as glycogen in the liver and muscles
Enhances protein synthesis
Stimulates the storage of fat in adipose tissue
Insulin is the counterpart to glucagon, working to lower blood glucose levels. Together, insulin and glucagon maintain a relatively stable blood glucose concentration.
The release of insulin is controlled by a negative feedback mechanism involving high blood glucose levels (hyperglycemia). When blood glucose rises, insulin is secreted to bring it back down.
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aldosterone
Name: Aldosterone
Source: Adrenal cortex (zona glomerulosa)
Target Cells: Kidneys
Functions:
Increases reabsorption of sodium and water in the kidneys
Decreases excretion of potassium in the kidneys
Helps regulate blood volume and blood pressure
Aldosterone is a mineralocorticoid hormone produced by the adrenal cortex. It plays a key role in maintaining fluid and electrolyte balance in the body.
The secretion of aldosterone is controlled by the renin-angiotensin-aldosterone system. When blood volume or pressure drops, this system is activated, leading to increased aldosterone release.
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glucocorticoid (cortisol)
Name: Glucocorticoids (primarily Cortisol)
Source: Adrenal cortex (zona fasciculata)
Functions:
Regulate metabolism, helping to increase blood glucose levels
Suppress immune system function and inflammatory responses
Facilitate the body's stress response
Influence growth, development, and behavior
Cortisol is the primary glucocorticoid hormone produced by the adrenal cortex. It has wide-ranging effects throughout the body, playing a crucial role in the body's stress response.
Cortisol secretion is controlled by a negative feedback loop involving the hypothalamus, pituitary gland, and adrenal cortex. Stress triggers the release of cortisol to help the body cope.
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estrogen
Source: Ovaries
Target: Many body cells
Function: Regulates female reproductive function
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Testosterone
Source: Testes
Target: Many body cells
Function: Regulates male secondary sex characteristics and sperm production
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Epinephrine
Source: Adrenal Medulla
Target: Many body cells
Function: Fight or flight response
Increases Heart Rate: Epinephrine makes the heart beat faster and stronger, which boosts blood flow to muscles and vital organs.
Expands Airways: It relaxes the muscles around the airways in the lungs, allowing you to breathe easier and take in more oxygen.
Raises Blood Sugar Levels: Epinephrine triggers the release of glucose (sugar) from the liver, providing quick energy for muscles.
Boosts Blood Pressure: It constricts blood vessels, especially in areas like the skin, which raises blood pressure to ensure essential organs are well-supplied.
Enhances Alertness: It makes you more mentally alert and sharp, helping you respond quickly to danger or challenges.
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Norepinephrine
Source: Adrenal Medulla
Target: Many body cells
Function: Causes vasoconstriction in skin, viscera, and skeletal muscles
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progesterone
Source: Ovaries
Target: Many body cells
Function: Promotes the storage of glycogen and further growth of blood vessels in the endometrium, which in pregnancy becomes the placenta. Also helps maintain pregnancy.
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Androgens
Definition: A class of hormones that are important for male sexual development and function
Source: Primarily produced in the testes, but also in smaller amounts by the adrenal glands
Functions:
Regulate production of sperm
Stimulate development of male secondary sex characteristics (e.g. facial/body hair, deepening of voice)
Contribute to libido (sex drive)
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Inhibin
source: Testes and Ovaries
Target: Anterior Pituitary
Function: Inhibits secretion of Follicle-Stimulating Hormone (FSH)
Inhibin is a hormone produced by the gonads (testes in males, ovaries in females). Its main function is to provide negative feedback to the anterior pituitary gland, inhibiting the release of Follicle-Stimulating Hormone (FSH).
By reducing FSH levels, inhibin helps regulate sperm production in males and the menstrual cycle in females. This is an important part of the endocrine system's feedback mechanisms to maintain hormonal balance.
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melatonin
Source: Pineal Gland
Target: Many body cells
Function: Helps regulate circadian rhythms and the sleep-wake cycle
Melatonin is a hormone produced by the pineal gland in the brain. Its main function is to help regulate the body's internal clock and sleep-wake cycles. increases as it gets dark outside
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Prostaglandins
Source: Prostaglandins are produced from arachidonic acid in cell membranes throughout the body.
Target: Prostaglandins have local effects on the cells near where they are produced.
Functions: Prostaglandins regulate inflammation, blood flow, smooth muscle contraction, sleep-wake cycles, and kidney/electrolyte balance.
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Leukotrienes
Source: Leukotrienes are produced from arachidonic acid in activated immune cells, particularly white blood cells.
Target: Leukotrienes target nearby cells involved in the inflammatory response, such as other immune cells.
Functions: The main roles of leukotrienes are to promote inflammation, constrict smooth muscle, increase vascular permeability, and attract more immune cells to sites of inflammation.
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thymosin
Source: Thymosin is produced and released by the thymus gland, a lymphoid organ located in the upper chest.
Target: The target cells for thymosin are T lymphocytes, a type of white blood cell important for immune function.
Functions: The main roles of thymosin are to promote the production and maturation of T cells, enhance the activity of mature T cells, help the immune system fight infections and diseases, and potentially slow the aging process.
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Gastrin
Source: Gastrin is produced by G cells located in the lining of the stomach and duodenum (first part of the small intestine).
Target: The target cells for gastrin are the parietal cells in the stomach lining.
Functions: The main roles of gastrin are to stimulate the secretion of gastric acid by parietal cells, promote growth and development of the stomach lining, increase stomach motility, and help regulate the overall digestive process.
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GIP
Name: GIP stands for Glucose-Dependent Insulinotropic Peptide
Source: GIP is produced by K cells located in the duodenum and jejunum (parts of the small intestine)
Target: The target cells for GIP are the pancreatic beta cells
Function: The main role of GIP is to help regulate blood glucose levels by stimulating the release of insulin from pancreatic beta cells in response to the presence of glucose. GIP also slows gastric emptying to further control blood glucose.
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Secretin
Source: Secretin is produced by S cells located in the duodenum (first part of the small intestine)
Target: The target cells for secretin are the pancreatic acinar cells and cells lining the bile ducts and gallbladder
Functions: The main roles of secretin are to stimulate the pancreas to secrete bicarbonate-rich juice, stimulate the liver to secrete bile, help regulate the pH of the small intestine by neutralizing stomach acid, and slow the rate of gastric emptying to allow more time for digestion.
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CCK
Name: CCK stands for Cholecystokinin
Source: CCK is produced by I cells located in the duodenum and jejunum (first and second parts of the small intestine)
Target: The target cells for CCK include the gallbladder, pancreas, and stomach
Functions: The main roles of CCK are to stimulate the gallbladder to release stored bile, stimulate the pancreas to secrete digestive enzymes, slow the rate of gastric emptying to allow more time for digestion, and promote a feeling of fullness and satiety after eating.
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Erythropoietin (EPO)
Source: Erythropoietin (EPO) is produced by the kidneys.
Target: EPO travels through the bloodstream and targets the bone marrow.
Function: In the bone marrow, EPO stimulates the production of new red blood cells. This helps maintain normal oxygen levels in the body, as red blood cells are responsible for carrying oxygen.
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ANP
Atrial Natriuretic Peptide (ANP) is produced by the heart.
Target: ANP travels through the bloodstream and targets the kidneys.
Function: In the kidneys, ANP helps decrease blood pressure by increasing the excretion of sodium and water. This helps lower the overall volume of fluid in the body, reducing blood pressure.
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Leptin
Source: Leptin is produced by adipose (fat) tissue.
Target: Leptin travels through the bloodstream and targets the brain, specifically the hypothalamus.
Function: In the hypothalamus, leptin helps suppress appetite. Leptin may also increase the activity of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are important for regulating reproductive function.
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hCG
Name: Human chorionic gonadotropin (hCG)
Source: hCG is produced by the placenta during pregnancy.
Target: hCG travels through the bloodstream and targets the ovaries.
Function: In the ovaries, hCG stimulates the continued production of the hormones estrogen and progesterone. These hormones are crucial for maintaining the pregnancy.
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renin-angiotensin-aldosterone pathway (RAAS)
The RAAS pathway is an important hormonal system for regulating blood pressure and fluid balance in the body.
1. Decreased blood pressure or blood volume triggers the kidneys to release the enzyme renin.
2. Renin converts angiotensinogen (from the liver) into angiotensin I.
3. Angiotensin converting enzyme (ACE) in the lungs converts angiotensin I into angiotensin II.
4. Angiotensin II stimulates the adrenal cortex to release the hormone aldosterone.
5. Aldosterone acts on the kidneys to increase sodium and water reabsorption, raising blood pressure and fluid levels.
This pathway helps the body respond to low blood pressure or low blood volume by increasing fluid retention and blood pressure through the actions of renin, angiotensin, and aldosterone.
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the steps and stages of a stress response
The initial fight-or-flight response is triggered by the sympathetic nervous system and adrenal medulla. This quickly mobilizes the body's resources for immediate physical activity, like fleeing from a threat.
The slower resistance reaction helps the body continue fighting the stressor long after the initial fight-or-flight response. This involves the hypothalamus-pituitary-adrenal axis.
The eventual exhaustion stage occurs if the resistance stage fails to combat the stressor. Prolonged exposure to high stress hormone levels can have negative health consequences.
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two main types of stress:
Physical stress - This threatens the survival of tissues, like extreme cold, prolonged exercise, or infections.
Psychological stress - This results from real or perceived dangers, including emotions like anger, depression, fear, and grief. Even pleasant stimuli can cause psychological stress.
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The body's response to stress involves:
The body's response to stress involves:
The hypothalamus controlling the general stress syndrome
Increased sympathetic activity and secretion of hormones like cortisol, glucagon, growth hormone, and antidiuretic hormone
These responses are designed to maintain homeostasis and help the body adapt to the stressor
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the effects of aging on the endocrine system
Production of many hormones, like growth hormone, thyroid hormones, and sex hormones, decreases with age.
Blood levels of other hormones, such as PTH, TSH, LH, and FSH, tend to increase with aging.
The pancreas releases insulin more slowly and cells become less sensitive to glucose as we get older.
The thymus gland shrinks in size after puberty and is replaced by fat and connective tissue.
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the olfactory process from the nose to the brain
The olfactory epithelium is located in the upper part of the nasal cavity. It contains olfactory receptor cells that have cilia (tiny hair-like projections) that stick out into the nasal cavity.
When you smell something, chemicals in the air stimulate the olfactory receptor cells. This creates an electrical signal.
The olfactory receptor cell axons (nerve fibers) extend through the cribriform plate of the ethmoid bone and form the olfactory (cranial nerve I) nerves.
The olfactory nerves carry the electrical signals to the olfactory bulbs at the base of the brain.
From the olfactory bulbs, the signals travel through the olfactory tract to the olfactory cortex in the temporal lobe of the brain, where the sense of smell is perceived and interpreted. 🧠
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what do the olfactory receptors in the olfactory epithelium (upper nasal cavity) do
These receptors detect different odor molecules in the air.
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The olfactory nerves (cranial nerve I)
These nerves carry the electrical signals from the olfactory receptors to the brain.
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The olfactory bulbs at the base of the brain
The olfactory nerves connect to the olfactory bulbs, where the signals are processed.
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olfactory glands
👃 The olfactory glands are located in the olfactory epithelium, which is the tissue that lines the upper part of the nasal cavity.
🧪 These glands secrete a thin layer of mucus over the olfactory receptors. This mucus helps to dissolve odor molecules so they can bind to the receptors.
💧 The olfactory glands also produce watery fluid that helps to keep the olfactory receptors moist and functioning properly.
🧠 The olfactory glands are important because they create the optimal environment for the olfactory receptors to detect and transmit smell information to the brain.
👨🔬 Without the olfactory glands, the olfactory receptors would dry out and not be able to do their job of sensing different smells.
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gustatory receptor cells
👅 The gustatory receptor cells are located in the taste buds on your tongue and other parts of your mouth.
🍔 When you eat food, the chemicals in that food dissolve in the saliva and come into contact with the gustatory receptor cells.
🧪 The receptor cells have specialized proteins on their surface that can bind to specific taste molecules, like sweet, sour, salty, bitter, and umami.
🧠 When the taste molecules bind to the receptors, it causes the gustatory receptor cells to generate electrical signals.
🧠 These electrical signals are then sent to the gustatory cortex in your brain, which allows you to perceive and identify different tastes.
👨🔬 The gustatory receptor cells are constantly being replaced, as they only live for about 10 days before being renewed.
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The olfactory epithelium contains 3 main types of cells:
Olfactory receptor cells - These are the cells that detect odors and send signals to the brain.
Supporting cells - These cells provide structure and support for the olfactory receptor cells.
Basal cells - These are stem cells that can replace the olfactory receptor cells when they die.
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what happens when looking at something close up
your eye lens changes shape, your pupils get smaller, and your eyes converge - all to help focus the image clearly on your retinas
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what happens when looking at something far away
when you look at something far away, your eye lens changes shape, your pupils get bigger, and your eyes diverge
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rhodopsin
Rods are very sensitive to light and allow you to see in dim lighting conditions, but only in shades of gray, not color.
Rhodopsin is the photopigment that allows rods to detect and respond to light.
When rhodopsin absorbs light, it undergoes a structural change that triggers a nerve impulse to be sent to your brain.
Rhodopsin is usually nonfunctional in bright daylight conditions. Your cones, which contain different photopigments, take over for color vision in bright light.
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two main parts of the inner ear
The outer bony labyrinth provides the structural framework and fluid-filled space for the inner membranous labyrinth.
The inner membranous labyrinth contains the specialized sensory receptors that detect sound waves and head/body movements for hearing and balance. 🧠👂
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otitis media
otitis media is a middle ear infection that can be common in young kids, but is treatable with the right medical care.
It occurs when the Eustachian tube, which connects the middle ear to the throat, becomes blocked or swollen
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Ménière’s disease
Ménière's disease is a disorder that affects the inner ear and can cause debilitating episodes of vertigo, hearing problems, and a feeling of pressure or fullness in the affected ear
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barotrauma
Barotrauma refers to an injury caused by a difference in pressure between the inside and outside of the body.
When it comes to the ears, barotrauma can occur during activities like:
Flying in an airplane
Scuba diving
Going up or down in an elevator
Here's what happens with ear barotrauma:
As the pressure changes, it can't be equalized quickly enough between the middle ear and the outside environment.
This pressure difference causes the eardrum (tympanic membrane) to bulge inward or outward.
This can be painful and can even rupture the eardrum in severe cases.
Symptoms of ear barotrauma include:
Ear pain
Ringing in the ears
Hearing loss
Dizziness
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glaucoma
glaucoma is a serious eye condition caused by increased pressure inside the eye that can lead to vision loss if not properly managed.
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The pituitary gland
is a small, pea-sized endocrine gland located at the base of the brain. It's often called the "master gland" because it produces hormones that regulate many important bodily functions.
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the pituitary glands tow main lobes
The anterior pituitary produces 7 major hormones, including:
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
The posterior pituitary stores and releases two hormones produced in the hypothalamus:
Oxytocin
Antidiuretic hormone (ADH)
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calcitriol
calcitriol is the active vitamin D hormone that regulates calcium and phosphate levels in the body
Increases the absorption of calcium and phosphate from the intestines 🍴
Increases the reabsorption of calcium in the kidneys 💦
Stimulates the release of calcium from the bones 🦴
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adrenal cortex
The adrenal cortex is the outer layer of the adrenal glands, which sit on top of the kidneys. 🏥
The adrenal cortex is divided into three main zones:
The outer zona glomerulosa - This zone secretes mineralocorticoids, like aldosterone, which help regulate sodium, water, and potassium balance in the body. 💧
The middle zona fasciculata - This zone secretes glucocorticoids, like cortisol, which help regulate metabolism, immune function, and the stress response. 🧠
The inner zona reticularis - This zone secretes androgens, which are male sex hormones that can be converted to estrogen in other tissues. 👨
