Nervous System Flashcards
(136 cards)
1
Q
What is the function of the nervous system?
A
To integrate and control the other body systems through the activities of the central and peripheral nervous systems. The nervous system receives and processes information and sends out signals to the muscles and glands to elicit an appropriate response.
2
Q
What structures constitute the Central nervous system? And what structures protect them?
A
The brain and the spinal cord, protected by the skull and the vertebrae, respectively.
3
Q
How do the central nervous system and the peripheral nervous system interact?
A
The central nervous system can send/receive signals from the peripheral nervous system, which connnects all parts of the body to the central nervous system.
4
Q
What does the peripheral nervous system consist of ?
A
All the nerves of the body that are in the brain or the spinal cord. The peripheral nervous system includes the cranial nerves and(spinal nerves)
5
Q
2 divisions of the peripheral nervous system
A
The motor/efferent and the Sensory/afferent
6
Q
Describe the movement of nerve impulses in the peripheral nervous system.
A
The peripheral nervous system receives impulses from the sensory organs through the sensory/afferent division and then relays impulses/signals to muscles/glands from the central nervous system through the motor/efferent division.
7
Q
2 divisions of the efferent division of the peripheral nervous system
A
Somatic and Autonomic
8
Q
What does the somatic and autonomic nervous system respectively control?
A
The somatic nervous system controls the skeletal muscles, joints and skin. The autonomic nervous system controls the smooth muscles of internal organs and the gland.
9
Q
2 Divisions of the autonomic nervous system
A
Sympathetic and Parasympathetic
10
Q
What is the function of the sympathetic nervous system?
A
The sympathetic nervous system activates and prepares the body for vigorous muscular activity, stress, and emergencies.
11
Q
What is the function of the parasympathetic nervous system?
A
The parasympathetic system lowers activity, operates during normal situations, permits digestion, and conserves energy.
12
Q
List 3 unusual characteristics of neurons.
A
Neurons (nerve cells) do not undergo mitosis and can last a lifetime.
Can live only for minutes without oxygen
Vary in size and shape
need large amounts of fuel
13
Q
Descrive the structure and function of the neuron cell body?
A
The neuron cell body contains all the organelles found in other body cells, except for centrioles, since nerve cells do not undergo mitosis. The cell body synthesizes all nerve cell products.
The cell body produces neurotransmitters which are sent to the axon terminals. These neurotransmitters relay signals across the axon terminal to the dendrites of adjacent cells.
14
Q
What are the 3 parts of a neuron?
A
The dendrites, the cell body and the axon
15
Q
Structure and function of the dendrite
A
The dendrite are short, branchlike extensions from the cell body that receive information from adjacent nerve cells while conducting these impulses towards the cell body.
16
Q
Descrive the axon
A
There is a single axon in each neuron. Axons serve to transmit the signal away from the cell body to the axon terminals and to the dendrites of other nerve cells.
The axon consists of cells similar to the cell body but they lack rough endoplasmic reticulum, so they must depend on the cell body for all necessary proteins.
17
Q
Composition and function of Schwann cells
A
Schwann cells are composed mostly of a white fatty layer called the myelin shealth, which is wrapped around the axon. Myelin shealths provide insulation of the nerve fiber and increases the speed of nerve impulses.
18
Q
Where are the Nodes of Ranvier located and what is their function?
A
Nodes of Ranvier are located between each myelin shealth on the axon. It is a gap between adjacent Schwann cell insulating sections. At these points the nerve impulse is forced to jump the gap. This increases the speed of the nervous impulse
19
Q
What important organelle is absent from the neuron cell body and what does the absence of this organelle indicate about activity of the cell body?
A
The absence of centrioles indicates that there is no cell division activity. Mitosis is not undergone by nerve cells.
20
Q
What are neurotransmitters?
A
One of the main functions of the cell body is to manufacture neurotransmitters, which are chemicals stored in secretory vesicles at the end of axon terminals. When neurotransmitters are released by the axon terminal vesicles, they participate in the transmission of the nerve impulse from one neuron to another.
21
Q
What does a nerve consist of ?
A
A nerve consists of hundreds of thousands of axons wrapped together in a connective tissue.
22
Q
What does “ganglia” refer to ?
What about neuroglial cells ?
A
In the peripheral nervous system the cell bodies of neurons are grouped together in masses called ganglia which are part of a single nerve. The neurons are also accompanied by non-nerve “supporting” cells known collectively as neuroglial cells which include oligodendrocytes, astrocytes, ependymal cells and microglial cells.
23
Q
What are each of the functions for the non nerve supporting cells AKA the neuroglial cells?
A
The functions of these supporting cells are as follows: ependymal cells (circulate cerebrospinal fluid and allow fluid exchange between brain, spinal cord and CSF), oligodendrocytes (insulation of central nervous system axons), astrocytes (control chemical environment of neurons) and microglial cells (protect CNS by scavenging dead cells and infectious microoganisms).
24
Q
How can neurons be classified ?
A
According to their structure and function
25
Neurons classified according to structure ?
Structurally, neurons are classified according to the number of extension from their cell body, as multipolar, bipolar and unipolar neurons. Multipolar neurons, the most common type in humans found as motor neurons or interneurons within the CNS, have three or more extensions, one axon and many dendrites. Bipolar neurons, found as receptors cells in the visual and olfactory systems, have two extensions, one axon and one dendrite. Unipolar neurons, found as sensory neurons in the peripheral nervous system, have one extension which branches into two, one central process running to the CNS and another peripheral process running to the sensory receptor.
26
How are neurons classified according to function ?
Functionally, neurons are classified as sensory or afferent neurons, motor or efferent neurons and association or interneurons. Most sensory neurons are unipolar and carry impulses from receptors in the skin or internal organs toward the CNS. Most motor neurons are multipolar and carry impulses from the central nervous system to muscle fibers or glands. Interneurons are usually multipolar and found within the central nervous system only. They transmit impulses between sensory and motors neurons conveying messages between various parts of the central nervous system, such as from one side of the brain or spinal cord to the other, or from the brain to the spinal cord, and vice versa.
27
What is the technical term used to describe a nerve impulse and what causes the impulse?
A nerve impulse is called an action potential and is caused by the movement of unequally distributed ions on either side of an axon’s plasma membrane.
28
An axon's membrane is polarized with a resting potential of -70 mV. Explain what this means and what maintains this resting potential.
The axon plasma membrane is polarized, meaning that one side has a different charge than the other side. This difference called a resting potential means that the charge on the inside of the axon's cell membrane is 70 millivolts less than the outside of the membrane. A sodium- potassium pump using active transport carries ions across the plasma membrane and because three Na+ ions are pumped out as two K+ ions are pumped in a relative positive charge develops and is maintained on the outside of the membrane
29
Stages of the Action Potential
1. Resting Potential
2. Depolarization
3. Repolarization
4. Afterpolarization
30
Describe what happens to the charges on the axon cell membrane during depolarization and what causes this to happen
During the resting phase both sodium and potassium gates that control the relative charges on sides of the membrane are closed. During depolarization the sodium gates open and sodium rushes into the axon and the inside becomes more positive than the outside causing the membrane potential to become more positive.
31
Describe what happens to the charges on the axon cell membrane during repolarization and what causes this to happen.
During repolarization the sodium gates close and potassium gates open allowing potassium to rush out of the axon. This returns a negative charge to the inside of the axon re-establishing the negative potential.
32
What happens in repolarization stage of the action potential?
The potassium gates that open during repolarization are slow to close and there is generally an afterpolarization undershoot of the potential
33
What causes the difference in intensity of a sensation?
The difference in intensity of a sensation is due to the number of neurons stimulated and the frequency with which they are activated. There is no difference in the intensity of any individual nerve impluse.
34
How is an impulse passed from one nerve cell to another?
There is a minute fluid-filled space, called a synapse, between the axon terminal of the sending neuron and the dendrite of the receiving neuron. When a nerve impulse reaches the end of an axon, neurotransmitters are released into the synapse. These bind with a receptor on the next neuron, opening Na+ gates in the receiving dendrite which causes depolarization and the impulse is carried.
35
Do neurons touch? Impulses passing from one nerve cell to another move \_\_\_\_\_\_\_\_\_\_
No they do not touch. _In only one direction_ Between every axon terminal of the sending neuron (presynaptic) and the dendrite of the receiving (postsynaptic) neuron there is a small fluid filled space called a synapse where the electric impulse must be transmitted by chemicals called neurotransmitters.
36
How do neurotransmitters transmit the signal?
The transmission of nerve impulses is electrochemical in nature as chemicals called neurotransmitters allow the signal to jump the synaptic gap. When a nerve impulse reaches the end of an axon, **voltage-gated calcium channels open**. As **Ca+2** rushes in, it causes vesicles containing the neurotransmitter to fuse with the plasma membrane and **release the neurotransmitter into the synapse.** When the neurotransmitter released binds with a receptor on the next neuron, **Na+ channels in the receiving dendrites open. Depolarization occurs** and the impulse is carried.
**Acetylcholine and norepinephrine** are well-known neurotransmitters, active in both the peripheral nervous system and the central nervous system. Once a neurotransmitter has been released into a synapse, it has only a short time to act. Some synapses contain enzymes that rapidly inactivate the neurotransmitter. For example, the enzyme acetylcholinesterase, or simply cholinesterase, breaks down acetylcholine. In other synapses, the synaptic ending rapidly absorbs the neurotransmitter, possibly for repacking in synaptic vesicles or for chemical breakdown. The short existence of neurotransmitters in the synapse prevents continuous stimulation (or inhibition) of postsynaptic membranes.
37
What prevents continuous stimulation of a nerve synapse and how is this accomplished?
The short existence of neurotransmitters in the synapse prevents continuous stimulation. Some synapses contain enzymes that rapidly inactivate neurotransmitters and other synapses rapidly absorb the neurotransmitter.
38
The peripheral nervous system is made up of \_\_\_\_\_\_\_\_\_
The peripheral nervous system lies outside the central nervous system. The peripheral nervous system is made up of nerves, which are part of either the somatic system or the autonomic system. The somatic system contains nerves that control skeletal muscles, skin, and joints. The autonomic system contains nerves that control the smooth muscles of the internal organs and the glands
39
How many pairs of cranial nerves are there ? What do they control?
There are 12 pairs of cranial nerves and, with the exception of the vagus nerve which controls the internal organs, the cranial nerves control the head, neck and face.
On Old Olympus Towering Tops A Fat Vivacious German Vends Anheiser Hops
Some Say Marry Money But My Brother Says Big Boats Matter More (To remember which cranial nerves are sensory, motor or both in function )
40
How many pairs of spinal nerves are there ?
There are 31 pairs of spinal nerves There are eight pairs of cervical (cranial) nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves.
41
How does each spinal nerve emerge from the spinal cord ?
spinal nerve emerges from the spinal cord by two short branches, or roots, which lie within the vertebral column. The dorsal root contains the axons of afferent sensory neurons, which conduct impulses to the cord. The ventral root contains the axons of efferent motor neurons, which conduct impulses away from the cord. These two roots join just before a spinal nerve leaves the vertebral column. Therefore, all spinal nerves are mixed nerves that take impulses to and from the spinal cord.
42
Describe the detail the structure of spinal nerves after leaving the vertebral column
Almost immediately after immerging from the vertebral column, a spinal nerve divides into branches called the dorsal ramus and ventral ramus. The smaller dorsal ramus contains nerves that serve the dorsal portions of the trunk carrying visceral motor, somatic motor, and sensory information to and from the skin and muscles of the back. The larger ventral ramus contains nerves that serve the remaining ventral parts of the trunk and the upper and lower limbs carrying visceral motor, somatic motor, and sensory information to and from the body surface, structures in the body wall, and the limbs.
43
What is a nerve plexus?
Some ventral rami merge with adjacent ventral rami to form a nerve plexus, a network of interconnecting nerves. Nerves emerging from a plexus contain fibers from various spinal nerves, which are now carried together to some target location. Major plexuses include the cervical, brachial, lumbar, and sacral plexuses
44
What is the most important nerve of the cervical plexus and what structure does it supply?
The phrenic nerve is the most important nerve of the cervical plexus and supplies both motor and sensory fibers to the diaphragm. Irritation of this nerve causes hiccups and severing this nerve would cause paralysis of the diaphragm and require use of a ventilator (mechanical respiratory). The saying “three, four, five keeps the diaphragm alive” is an easy way to remember that the phrenic nerve arrives from the ventral rami of C3-C5.
45
What are the nerves that form the brachial plexus?
Axillary nerve
Radial nerve
Median nerve
Musculocutaneous nerve
Ulnar Nerve
46
What muscles does the axiliary nerve innervate ?
The axillary nerve supplies three muscles: the deltoid (a muscle of the shoulder), the teres minor (one of the rotator cuff muscles) and the long head of the triceps brachii (an elbow extensor). The axillary nerve also carries sensory information from the shoulder joint
47
What is innervated by the radial nerve ?
The radial nerve supplies the triceps brachii muscle of the arm, as well as 12 muscles in the forearm and the associated joints and overlying skin.
48
What is innervated by the medial nerve? What is affected by compression of this nerve?
The median nerve supplies flexor muscles of the forearm and the skin of the first three and a half fingers. Compression of the median nerve in the carpal tunnel causes carpal tunnel syndrome or decreased sensation in the first three and a half fingers.
49
What is innervated by the musculocutenous nerve?
The musculocutaneous nerve supplies the flexor muscles of the arm.
50
What is innervated by the ulnar nerve? If damaged, what can happen?
The ulnar nerve supplies part of the flexor muscles of the forearm, wrist, and hand as well as the skin of half the ring finger and pinky finger. If the ulnar nerve is damaged it results in a condition known as claw hand, the inability to open the fourth and fifth fingers.
51
What is the major nerve that arises from the Lumbar Plexus and what does it innervate ?
The Lumbar plexus nerves arise from the ventral rami of L1-L4 and the femoral nerve is the major nerve that comes from this plexus. The femoral nerve supplies the hip flexors and knee extensors as well as sensation to the skin of the anterior thigh
52
What is the major nerve that arises from the sacral plexus ?
the sacral plexus nerves arise from the ventral rami of L4-S4 and the sciatic nerve is the major nerve that comes from this plexus. The sciatic nerve is the largest nerve in the human body. It supplies the inferior trunk and posterior surface of the thigh. Increased pressure on this nerve can result in the condition known as sciatica.
53
What does the somatic nervous systme consist of ?
The somatic nervous system includes all nerves that serve the musculoskeletal system and the exterior sense organs, including the skin. Exterior sense organs (and skin) are receptors, which receive environmental stimuli and then initiate nerve impulses. Muscle fibers are effectors, which bring about a reaction to the stimulus.
54
What are reflexes?
Reflexes are nearly instantaneous, automatic, involuntary motor responses to stimuli occurring inside or outside of the body.
Reflexes may be subconscious as the regulation of blood sugar by the hormones, may be noticeable as shivering in response to a drop in body temperature; or may be obvious as touching a very hot object and immediately withdrawing your hand. Some reflexes, such as blinking the eye, involve the brainstem, but others, such as the flexor reflex involved when withdrawing your hand from the hot object involve only the nerves and the spinal cord in an action known as the reflex arc
55
Explain why a reflex arc occurs so quickly and why this speed is necessary?
A reflex arc occurs so quickly because there is no immediate brain processing. The action involves only nerves and the spinal cord... this speed is necessary because it protects us from injury as we can respond immediately, without first consciously perceiving the threat.
56
What are the five components of the reflex arc ?
A reflex arc is the neural pathway that a nerve impulse follows.
1) Receptor at end of a sensory neuron
2) Sensory neuron conducts nerve impulses along an afferent pathway toward the Central nervous system
3) Integration center containing one or more synapses in the CNS
4) Motor Efferent Neuron conducts nerve impulses along an efferent pathway from the integration center to an effector
5) The effector responds by contracting (muscle) or secreting a product (gland)
57
Why do spinal reflexes occur much faster than ones involving the brain?
It involves fewer neurons. Also the electrical signal does not have to travel to the brain and back. There is a shorter distance traveled by afferent and motor neurons if only going to and back from the spinal cord.
58
What happens along the nerve pathway when you touch a blazing object?
If you touch a very hot object, a receptor in the skin generates nerve impulses, which move along the dendrite of a sensory neuron toward the cell body and the central nervous system. The cell body of a sensory neuron is located in the dorsal-root ganglion just outside the spinal cord. From the cell body, the impulses travel along the axon of the sensory nerve. The impulses then pass to many interneurons, one of which connects with a motor neuron. The short dendrites and the cell body of the motor neuron lead to the axon, which leaves the cord by way of the ventral root of the spinal nerve. The nerve impulses travel along the axon to muscle fibers, which then contract so that you withdraw your hand from the hot object. This whole series of responses occurs because the sensory neuron stimulates several interneurons. They take impulses to all parts of the central nervous system, including the cerebrum, which in turn makes the person conscious of the stimulus and the reaction to it.
59
Spinal reflexes only travel to the __________ and back .
Spinal cord
60
What is an example of a spinal reflex ?
the flexor reflex (withdrawal of your hand from a very hot object) and the stretch reflex on an opposing muscle to prevent over-stretching of its antagonist.
61
Stretch reflexes
protect the muscle against increases in length which may tear or damage muscle fibers. They are important for maintaining upright posture in humans. fibers. The patellar reflex is an example, which is the stretch reflex of the quadriceps femoris muscle in your thigh- it prevent the over-stretching of the quadriceps. The patellar tendon attaches the quadriceps muscle to the tibia bone of the lower leg. The quadriceps is an extensor muscle raising the lower leg as it contracts thereby extending the angle of the knee joint. Tapping the patellar tendon stretches the quadriceps muscle and causes the sensory nerve receptor of the muscle to send a signal along the afferent neuron to the spinal cord. This causes the efferent neuron to return a signal to the quadriceps muscle to contract and lift the lower leg.
62
The autonomic nervous system is made up of what ?
motor neurons that control the internal organs automatically and usually without need for conscious intervention. The sensory neurons that come from the internal organs allow us to feel internal pain. The cell bodies for these sensory neurons are in dorsal-root ganglia, along with the cell bodies of somatic sensory neurons.
63
What is the antagonistic effect of the 2 divisions of the autonomic nervous system upon a visceral organ?
There are two divisions of the autonomic system: the sympathetic and parasympathetic systems. Both of these function automatically and usually subconsciously in an involuntary manner. These two divisions cause essentially opposite effects on the same visceral organ; if one stimulates, the other inhibits.
64
Sympathetic nervous system effects
**_Sympathetic effect_**
**eye**
*dilates pupils*
**glands (salivary, pancreas)**
*inhibits secretion*
**sweat glands**
*stimulates sweating*
**heart (muscle)**
*increases heartbeat*
**heart blood vessels**
*dilates vessels*
**lungs**
*dilates bronchioles*
**digestive tract**
*decreases activity
constricts sphincters*
**liver**
*epinephrine stimulates release of glucose*
**kidney**
*decreases urine output*
**vagina/clitoris**
*contracts vagina*
**penis**
*causes ejaculation*
**blood vessels**
*constricts blood vessels*
**cell metabolism**
*increases metabolic rate*
65
Effects of the Parasympathetic system
**_ParaSympathetic effect_**
**eye**
*constricts pupils*
**Glands (Salivary, pancreas)**
*stimulates secretion*
**sweat glands**
*no effect*
**heart (muscle)**
*slows heartbeat*
**heart blood vessels**
*no effect*
**lungs**
*constricts bronchioles*
**digestive tract**
* increases peristalis*
* relaxes sphincters*
**liver**
*no effect*
**kidney**
*no effect*
**vagina/clitoris**
*excites clitoris*
**penis**
*causes erection*
**blood vessels**
*no effect*
**cell metabolism**
*no effect*
66
List the four parts of the human brain.
The cerebellum,
the brain stem (mid brain, pons, medulla oblongata) t
the cerebral hemispheres
diencephalon (thalamus, hypothalamus and the epithalamus)
67
How many ventricles do the brains have and what are they ?
There are 4 ventricles in the interior spaces of the brain. They are chambers filled with cerebrospinal fluid which is produced there.
68
Functions of the medulla oblongata
A section of the brainstem that regulates the heartbeat and breathing, and blood pressure through vasoconstriction.
It also contains the reflex centers for vomiting, coughing, sneezing, hiccupping, and swallowing. The medulla contains tracts that ascend or descend between the spinal cord and the brain's higher centers.
69
Functions of the pons
The pons contains bundles of axons traveling between the cerebellum and the rest of the central nervous system. In addition, the pons functions with the medulla to regulate the breathing rate and has reflex centers concerned with head movements in response to visual and auditory stimuli
70
Functions of the midbrain
Aside from acting as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum, the midbrain has reflex centers for visual, auditory, and tactile responses.
71
Functions of the hypothalamus
The hypothalamus, forming the floor of the third ventricle, maintains homeostasis, or the constancy of the internal environment, and contains centers for regulating hunger, sleep, thirst, body temperature, water balance, and blood pressure. The hypothalamus controls the pituitary gland and thereby serves as a link between the nervous and endocrine systems.
72
Functions of the thalamus
The thalamus, in the roof of the third ventricle, is the last portion of the brain for sensory input before the cerebrum. It serves as a central relay station for sensory impulses traveling upward from other parts of the body and the brain to the cerebrum. It receives all sensory impulses (except those associated with the sense of smell) and channels them to appropriate regions of the cerebrum for interpretation.
73
Functions of the epithalamus
The epithalamus forms the roof of the third ventricle and is composed of the pineal body which secretes melatonin to control the wake-sleep cycle and the choroid plexus which produces cerebrospinal fluid.
74
All except what sensory impulses are channeled through the thalamus?
The sense of smell
75
What is the function of the choroid plexus?
Produces cerebrospinal fluid
76
What structure is this ? Describe its characteristics and where it is in the brain
The cerebellum, below and at the back of the brain, is convoluted and divided into two hemispheres with deep fissures subdividing it into three lobes. It is composed of a thin outer cortex of gray matter and internal white matter. The anterior and posterior lobes of the cerebellum act to coordinate body movements by receiving information from the body trunk and influence the motor activities of the trunk and shoulder and pectoral girdle muscles by relaying information to the cerebral motor cortex. The intermediate lobe coordinates limb movements. The cerebellum is also involved with planning movements, maintaining balance, controlling certain eye movements, maintaining normal muscle tone and maintaining posture
77
What is the largest part of the brain comprising about 83% of the brain mass?
The cerebrum- which is the foremost part of the brain.
It consists of two large masses called cerebral hemispheres, which are connected by a bridge of nerve fibers called the corpus callosum.
78
What is the outer portion of the cerebral hemispheres called ? Describe its structure
The outer portion of the cerebral hemispheres, the cerebral cortex, is highly convoluted and gray in color marked by raised ridges of tissue called gyri, separated by shallow grooves called sulci. The deeper grooves, called fissures, separate large regions of the brain.
Some of the deeper sulci divide each hemisphere into four surface lobes: frontal, parietal, temporal and occipital.
79
What do the median longitudinal fissure and the transverse fissure separate ?
The median longitudinal fissure separates the cerebral hemispheres from one another and the transverse fissure separates the cerebral hemispheres from the cerebellum.
80
What three kinds of functional areas does the cerebral cortex contain ?
motor areas that control voluntary motor functions
sensory areas that provide for conscious awareness of sensation
association areas that act mainly to integrate information for purposeful action.
81
Lobes of the cerebrum
82
What is the part of the brain that is responsible for consciousness and governs intelligence and reasoning ?
The cerebrum
83
What are the functions of each lobe of the cerebral hemispheres?
The frontal lobe controls motor functions and permits us to control our muscles consciously.
The parietal lobe receives information from receptors located in the skin, such as those for touch, pressure, and pain.
The occipital lobe receives and interprets visual input.
The temporal lobe has sensory areas for hearing and smelling.
84
Can the cerebrum affect activities of the lower part of the brain?
The cerebrum controls the activities of lower parts of the brain. The cerebrum can override the functioning of the brain stem and diencephalon, as when meditation or biofeedback helps control the heart rate. Acting on sensory input from the thalamus, the cerebrum initiates voluntary motor activities and controls the actions of the cerebellum.
85
What do association areas within each of the four lobes of the cerebral cortex allow us to do ?
These association areas allow each lobe to receive information from the other lobes and integrate it into higher, more complex levels of consciousness.
These are concerned with intellect, artistic and creative ability, learning, and memory.
86
What in tarnation is the limbic system?
The limbic system involves portions of both the unconscious and conscious brain. It lies just beneath the cerebral cortex and contains neural pathways that connect portions of the frontal lobes, the temporal lobes, the thalamus, and the hypothalamus. The basal nuclei, masses of gray matter that lie deep within each hemisphere of the cerebrum, are also part of the limbic system.
87
What is the limbic system known as ?
Our feeling brain since stimulation of different areas of the limbic system causes rage, pain, pleasure, or sorrow. The limbic system affects the emotional aspects of behavior, evaluates rewards and is important in motivation. Extensive connections between the limbic system and lower and higher brain regions cause acute emotional stress to produce visceral illnesses, such as stomach ulcers, high blood pressure, and irritable bowel syndrome.
88
How is the limbic system involved in learning and memory processes ?
The limbic system is also involved in the processes of learning and memory. Learning requires memory, but just what permits memory development is not definitely known. Investigators have been working with invertebrates such as slugs and snails because their nervous system is very simple and yet they can be conditioned to perform a particular behavior. To study this simple type of learning, it has been possible to insert electrodes into individual cells and to later record the electrochemical responses of these cells. This type of research has shown that learning is accompanied by an increase in the number of synapses, while forgetting involves a decrease in the number of synapses. In other words, the nerve-circuit patterns are constantly changing as learning, remembering, and forgetting occur. Within the individual neuron, learning involves a change in gene regulation and nerve protein synthesis and an increased ability to secrete transmitter substances.
Research indicates that the limbic system is absolutely essential to both short-term and long-term memory. An example of short-term memory in humans is the ability to recall a telephone number long enough to dial the number; an example of long-term memory is the ability to recall the events of the day. After nerve impulses circulate within the limbic system, the basal nuclei stimulate the sensory areas where memories are stored. The involvement of the limbic system certainly explains why emotionally charged events result in our most vivid memories. The fact that the limbic system communicates with the sensory areas for touch, smell, vision, and so forth accounts for the ability of a particular sensory stimulus to awaken a complex memory.
89
How is the brain protected ?
Neurons are not replaceable and are damaged by even the slightest pressure but the brain is protected by the skull of the skeletal system, membranes, a cushion of cerebrospinal fluid and the “blood-brain barrier”. The meninges are three connective tissue membranes that cover and protect central nervous system organs and enclose cerebrospinal fluid. The leathery dura mater is the double-layered outer meninx. The middle arachnoid meninx is a loose layer separated from the dura mater by the subdural space. Beneath the arachnoid meninx is the subarachnoid space which contains blood vessels and is filled with cerebrospinal fluid. The inner pia mater meninx is composed of connective tissue and is tightly attached to the brain. Cerebrospinal fluid (CSF), similar to and formed in the ventricles from blood plasma, cushions the brain and spinal cord by providing buoyancy. CSF is similar in composition to blood plasma, from which it arises by permeating through the choroid plexus capillaries. Once formed the CSF circulates through the ventricles and into the subarachnoid space bathing and floating the brain. The blood-brain barrier is due to the relatively impermeable brain capillaries which provide a stable chemical environment for the brain protecting it from variations which would cause uncontrollable firing of neurons.
90
What is a concussion ?
If your head is moving and then is suddenly stopped as it hits an object, brain damage can occur at the site of the impact and also as the brain hits the opposite side of the skull. A slight injury of this type is called a concussion since the symptoms are mild and transient including dizziness or brief loss of consciousness, but no permanent neurological damage is sustained
91
What is a brain contusion?
A more serious impact injury that results in significant tissue damage which usually causes unconsciousness (coma), ranging in duration from hours to a lifetime.
92
What can happen following blows to the head?
Hemorrhage can cause blood to accumulate increasing intracranial pressure and compressing brain tissue. If this pressure forces the brain stem into the foramen magnum, control of blood pressure, heart rate, and respiration is lost with possible fatal consequences.
Traumatic head injuries can also result in swelling of the brain due to water uptake by brain tissue.
93
What is the most common nervous system disorder?
**Stroke** Strokes occur when blood circulation to a brain area is blocked resulting in tissue death due to lack of oxygen and nutrients being supplied to brain cells. This is most often caused by a clot or fat deposit blocking a cerebral artery but can also be due to compression of brain tissue by hemorrhage or edema. Stroke victims often die but those who survive usually suffer paralysis, cognitive deficits, speech problems, emotional difficulties and pain. Some patients recover at least a portion of their lost faculties, because undamaged neurons sprout new branches that spread into the area of injury and take over some lost functions.
94
What are the effects of Alzheimers disease?
a progressive degenerative disease of the brain, usually seen in elderly people, that ultimately results in mental decline. Its victims exhibit early difficulty remembering newly learned information and then increasingly severe symptoms, including disorientation, mood and behavior changes; deepening confusion about events, time and place; unfounded suspicions about family, friends and caregivers; more serious memory loss and behavior changes; and difficulty speaking, swallowing and walking. Alzheimer’s disease is associated with structural changes in the brain, particularly in the cerebral cortex.
95
What is ALS?
Amyotrophic lateral sclerosis (ALS), Lou Gehrig’s diseaseis a neuromuscular condition that involves progressive destruction of anterior horn motor neurons and brain pyramidal tract fibers. As the disease progresses, the sufferer loses the ability to speak, swallow, and breathe; death typically occurs within 5 years.
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How does paralysis result ?
Paralysis (loss of motor function) or sensory losses is caused by any localized damage to the spinal cord or spinal nerve roots. Damage to the ventral root or anterior horn cells results in paralysis of the associated skeletal muscles since nerve impulses cannot reach these muscles which after time begin to atrophy. If the spinal cord is severed at any level, total motor and sensory loss is experienced in body regions below the site of the damage. Paraplegia, lower limb paralysis, occurs if the spinal cord is severed between T1 and L1. Quadriplegia, paralysis of all four limbs, occurs if the spinal cord is severed in the cervical region.
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How long is the spinal cord and where does it end?
about 17 inches in length and extends from the brain stem to the first lumbar vertebra
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What is the terminating point of the spinal cord called ?
**The conus medullaris**
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What is the cauda equina ?
The extension of the cord beyond L1 is a collection of nerve roots called the cauda equina which runs to its end at the coccyx.
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What does the spinal cord and its extensions enable ?
Its the means by which all impulses travel between the brain and the rest of the body by way of the set of 31 pair of spinal nerves.
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List the 3 protections for the spinal cord.
Vertebral Column, Meninges, Cerebrospinal Fluid
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Describe the protective layers of the spinal cord meninges
The outer meninx, a single layer called the spinal dural (mater) sheath is separated from the vertebral column by a cushioning fat-filled epidural space. The space between the middle arachnoid and inner pia mater meninges is filled with cerebrospinal fluid. An extension of pia mater runs from the conus medullaris to the coccyx where it provides the inferior anchor for the spinal cord. Because the cord ends at L1, the cerebrospinal filled subarachnoid space inferior to this point is the location chosen to perform a spinal tap removal of fluid for diagnostic testing.
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The spinal cord contains outer white matter and interior grey matter.
The surface of the spinal cord has two grooves: the anterior median fissure and the shallower posterior median sulcus. The interior gray matter of the cord is composed of a mixture of multipolar neurons and supporting cells. The outer white matter is composed of myelinated and un-myelinated nerve fibers. The gray matter of the cord consists of two posterior (dorsal) horns, two anterior (ventral) horns and much smaller anterior horns connected by a cross-bar called the gray commissure.
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1. Anterior Horn
2. Posterior Horn
3. Gray Commissure
4. Anterior Funiculus
5. Lateral Funiculus
6. Posterior Funiculus
7. Anterior Comissure
8. Anterior Median Fissure
9. Posterior Median Sulcus
10, Central Canal
11. Anterior Root
12. Posterior Root
13. Dorsal Root Ganglion
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The anterior (ventral) horns contain somatic motor neurons whose axons serve as efferent pathways to skeletal muscles by way of the ventral roots of the spinal cord. The lateral horn neurons contain autonomic sympathetic motor neurons whose axons serve as efferent pathways to visceral organs by way of the ventral roots of the spinal cord along with those of the somatic motor neurons. The posterior (dorsal) horns serve as one of the afferent pathways from receptors by way of the dorsal roots of the spinal cord.
The white matter fibers of the spinal cord are mostly composed of ascending tracts that proceed up to the brain carrying sensory inputs and descending tracts that proceed down to (or within) the cord carrying motor outputs with a few commissural tracts across the cord.
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What are the special senses?
The five special senses of vision, smell, taste, hearing and equilibrium (balance) are the senses that have specialized organs containing specialized receptor cells which carry their impulses by way of specialized somatic and visceral afferents.
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Is touch considered a special sense ?
No it is not because it does not have any specialized organ or receptors. It is a somatic sense.
It uses general receptors composed of modified dendrites of sensory neurons. Touch includes pressure, vibration, pain and heat and such information is carried in general somatic afferents and general visceral afferents.
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The eye contains 3 layers: the outer fibrous layer, the middle vascular layer and the interior sensory layer
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What structures comprise the outer fibrous layer of the eye ?
The outer fibrous layer includes the posterior portion known as the sclera and the anterior portion known as the cornea. The sclera is the “white of the eye”, the cornea is the transparent part of the eye where light enters.
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What comprises the middle vascular layer?
The middle vascular layer of the eye includes the darkly-colored posterior choroid which prevents light from dispersing throughout the eye and supplies blood to the other layers of the eye. The anterior ciliary body changes the shape of the lens allowing it to focus. The iris is anterior to the ciliary body and contains the colored pupil which controls the amount of light entering the eye by using its muscle fibers to contract or dilate based on the amount of light in the environment.
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What comprises the interior sensory layer?
The interior sensory layer includes the retina which contains two types of cells. The more numerous rods, our dim light and peripheral vision receptors which are more sensitive to light but do not generate sharp or color images. The cones operate in bright light generating sharp color images.
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Rods and cones are responsible for this respectively
They are the receptor cells within the retina that help us to see.
The more numerous rods, our dim light and peripheral vision receptors which are more sensitive to light but do not generate sharp or color images.
The cones operate in bright light generating sharp color images.
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What are the six mucles that control eye movements?
The **medial rectus, inferior rectus, superior rectus, and inferior oblique** are all innervated by the third cranial nerve, the oculomotor. The medial rectus turns the eye medially. The inferior rectus moves the eye medially and depresses it. The superior rectus moves the eye medially and elevates it. The inferior oblique moves the eye laterally and elevates it. The **fifth muscle is the superior oblique**, which is controlled by the fourth cranial nerve, the trochlear nerve, and moves the eye laterally and depresses it. Finally, **the sixth muscle, the lateral rectus**, is controlled by the sixth cranial nerve, the abducens, and turns the eye laterally.
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What is the pathway for light passing through the eye?
Light passes into eye moving progressively through the cornea, aqueous humor, lens and vitreous humor to the surface of the retina which sends a signal through the optic nerve on to the optic chiasm at the base of the hypothalamus. The medial fibers of the optic nerve cross to the other side when they reach the optic chiasm where the optic tracts are formed. As a result of this crossover of fibers, the right side of the brain receives signs from the lateral side of the right eye and the medial side of the left eye, and the situation is reversed for the left side of the brain. If the right optic nerve is damaged, the right eye will be unable to see. However, if the right optic tract is damaged this causes blindness in the left half of the field of vision in both eyes.
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The ear is the sensory organ for hearing and it can be divided into three areas: the external, middle, and inner ears
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What does the external ear consists of ?
The external ear consists of the auricle and the external acoustic canal (meatus). The auricle directs sound waves into the external acoustic canal so that they can be detected. It is the part of the ear that can be seen from the outside and is composed of elastic cartilage covered with thin skin making up the rim (helix) and the lobule that lacks cartilage. The external acoustic canal is the tunnel between the auricle and the eardrum and is composed of elastic cartilage near the auricle and a cylinder through the temporal bone. The canal is lined with skin containing hairs and glands that secrete earwax which traps foreign materials. The inner end of the acoustic canal terminates at the tympanic membrane (eardrum), a thin membrane of connective tissue whose vibration transmits sound energy to the middle ear.
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What does the middle ear consist of ?
The middle ear or tympanic cavity is an air-filled chamber containing the three smallest bones in the body which are known as the ossicles: the malleus (hammer), the incus (anvil), and the stapes (stirrup). The malleus receives the vibrations from the eardrum and transfers them along progressively through the incus to the stapes which conveys them to the inner ear.
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What does the iner ear consist of ?
The inner ear is composed of the bony labyrinth, a system of perilymph fluid-filled channels which contain the membranous labyrinth, a group of endolymph fluid-filled membranous sacs and ducts all of which is divided into three sections the vestibule, the semicircular canals and the cochlea.
**The cochlea, the vestibule and the semicircular canals**
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What is the function of the vestibule in the inner ear ?
What is the function of the the semicircular canals?
The vestibule houses receptors which provide the body's balance system.
The semicircular canals are the anterior vertical, posterior vertical and horizontal lateral canals which each contain at their junction an equilibrium receptor which respond to head movements, thereby contributing to the body's balance and orientation.
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What is the function of the cochlea?
he cochlea is a spiral, bony chamber containing the membranous endolymph-filled cochlear duct which houses the organ of Corti and terminates at the cochlear nerve. The organ of Corti contains tiny hairs which initiate an action potential that is transmitted through the cochlear nerve to the brain for processing.
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What is the hearing pathway and process?
Hearing is caused by (1) sound waves passing into the external auditory canal and (2) causing the ear drum to vibrate which (3) transmits the vibrations to the ossicles which (4) push against fluid in the cochlear duct which (5) causes the hairs in the organ of Corti to move which (6) stimulates nearby neurons to (7) send impulses through the cochlear nerve to the brain.
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3. Ausicle
4. Tympanic Membrane
6. Malleus
7. Incus
8. Stapes
9. Semicircular Canals
10. Cochlea
11. Cochlear Nerve
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Why is smell one of the chemical senses?
Smell is one of the chemical senses because its receptors are activated by airborne chemical substances dissolved in fluid on the nasal mucous membranes. Olfactory (smell) receptors are located in the olfactory epithelium on the roof of the nasal cavity.
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What does the olfactory epithelium contain?
millions of bipolar neuron receptor cells whose dendrite extends from the cell body to the surface of the epithelium where it terminates in a bulb from which arise many cilia called olfactory hairs.
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What do the olfactory layers extend into ?
The olfactory hairs extend into a thin layer of mucus covering the surface of the epithelium in which airborne chemical substances dissolve in order to be detected. Several unmyelinated axons of olfactory neurons collect to form olfactory nerve fiber bundles which pass through the ethmoid bone in the roof of the nasal cavity and synapse with the olfactory nerve tract in the olfactory bulb.
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What is any odor due to ?
a combination of many different chemical substances but smell has been defined as combinations of a limited number of primary odors.
One theory lists seven primary odors: floral (roses), ethereal dry cleaning fluid), camphoraceous (mothballs), musky (perfumes), pepperminty (mint gum), pungent (vinegar) and putrid (rotten eggs).
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Why is taste one of the chemical senses?
Because its receptors are activated by chemical substances dissolved in saliva. Taste receptors are located in taste buds mostly on the tongue but throughout the mouth. The taste buds are found as raised areas on the tongue
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What are the three types of epithilial cells that compose taste buds ?
Gustatory cells which are the chemoreceptors, supporting cells which form the bulk of the taste bud and separate the taste receptors cells from one another and the tongue epithelial cells and basal cells which serve as stem cells dividing and differentiating into supporting cells which then form new gustatory cells.
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What is the taste process?
Each taste bud sits in a taste pore from which long microvilli called gustatory hairs attached to the gustatory cells project into the saliva. Food chemicals contact the gustatory hairs which serve as the gustatory cell membranes generating an action potential in dendrites which are wrapped around the gustatory cells. The impulse is carried by afferent fibers to two cranial nerve pairs, the facial nerve and the glossopharyngeal nerve which transmit the impulse to the thalamus and ultimately to the parietal lobe.
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What are the five primary tastes?
**Sweet, salty, bitter, sour and savory**
Each of these tastes are produced by different chemicals found in the food
The sweet taste is produced by many compounds including sugars and some amino acids. The salty taste is produced by many metal salts, especially NaCl. The sour taste is produced by acids like acetic acid (in vinegar). The bitter taste is produced by many drugs like aspirin. The savory taste is due to chemicals such as the amino acid glutamate and is found in many foods like fish, ripe tomatoes, aged cheeses and soy sauce.
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Does smell have an effect on taste? What else contributes to taste sensation?
Yes. **Stimulation of olfactory (smell) receptors** has a great effect on the sensation of taste in addition to taste bud stimulation. When the **olfactory receptors** are obstructed by nasal congestion or other factors, taste is most often not able to be detected.
The mouth also contains **nociceptors** (pain) and t**hermoreceptors** (temperature) that contribute markedly to the taste experience of hot foods, both temperature-wise (hot tea) and taste-wise (hot peppers).
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Why is the action potential of a neuron self propagating or all or nothing ?
Because the change in membrane potentials trigger the ion channels in an adjacent area to open. It travels along the length of the axon like a wave.
It is self-propagating because the ion channels are prompted to open whenever the membrane potential decreases (depolarizes) in an adjacent area. An action potential is an all-or-nothing response either occurring or not.
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