Biology Sem 1 Year 12 Flashcards
- Define homeostasis.
The condition of a
relatively stable internal
environment, maintained
within narrow limits,
regardless of the external
environment
Describe the negative feedback loop
Stimulus
Pain, smell, heat. light, visuals, salt, sugar,
Anything in the environment that the body needs to react to
Receptor
The element that is detecting changes/the stimulus
Example:
Chemoreceptor detects chemical stimuli
Mechanoreceptor detects mechanical stimuli
Processing Centre
Takes message from the receptor
The message of the presence of the stimulus is carried around the body
Nervous System for short/sharp responses
Endocrine System for slower/longer responses
Effector
What carries the response
-Muscles and endocrine glands
Response
-What the body actually does
Stimulus-response mechanisms usually have a Negative Feedback stage, in which the response produced reduces the effect of the original stimulus
Example, after eating sugar, the body tries to reduce the sugar level
Identify the structures, processes and behaviours that allow homeostasis to be maintained.
Thermoregulation
-Thermoregulation is a stimulus response system that maintains the body’s core temp at a steady state
-The hypothalamus is the control centre for thermoregulation as it receives signals from external and internal cold and hot receptors. It initiates a response
-As a result, numerous mechanisms are activated to warm/cool body
-Initiates negative feedback to reduce the stimulus
Body can gain heat by:
-increase in metabolic processes
-shivering
-exercise/muscular activity
-radiation/conduction to body
Can lose heat by
-Evaporation of sweat
-Panting
-convection
-radiation and conduction away from body
Or increasing/ decreasing surface area
The pili muscle (hair on arms erecting or laying flat) (Piloerection)
Recall one example of how homeostasis is maintained in the human body.
Explain the importance of homeostasis.
to ensure the internal evironment is at a good point so that funciton and physiology of the body can continue
The variables of the body are maintained correctly
Temperature
Blood glucose
Water Daily intake
Ions
pH of arterial blood
Blood pressure – arterial
Describe the different types of receptors.
Chemoreceptor detects chemical stimuli
Mechanoreceptor detects mechanical stimuli
Photoreceptor-light
Thermoreceptor-hot/cold
Nociceptor-pain
Osmoreceptor-water
Explain that the responses to a stimulus involve; a stimulus, receptor, messenger, effectors and
response
(using the example of the body responding to a cold environment)
1.Stimulus: decrease in body temp below normal
2.Receptor: decrease detected by thermoreceptors in SKIN, ORGANS and HYPOTHALAMUS
3.Control Centre: hypothalamus sends signals via nerve and hormonal systems to effectors
- Effectors: Skeletal muscles, blood vessels near skin, body cells involved in metabolism, cerebral cortex (behavioural)
- Response:
shivering, vasoconstriction of skin vessels, behavioural changes, increased metabolic rate, change in behaviour
Recall the main components of the central and peripheral nervous system.
Central nervous system (CNS) and peripheral nervous system (PNS)
Central nervous system (CNS)
-brain and spinal cord
Peripheral nervous system (PNS)
-nerves
-messages to and from brain
Explain the role of the autonomic and somatic nervous systems in homeostasis.
Autonomic and Somatic are both in the Peripheral Nervous System and both use nerve cells
Peripheral nervous system activates specific glands/ muslces
The SNS and the ANS work together to regulate bodily function and provide reactions to external stimuli
Coordinate behaviour and respond to the external environment
The somatic nervous system: Contraction of Leg
Controls skeletal muscles (used for movement). (walking)
Instructions generally originate from the primary
motor cortex of the brain.
Controls voluntary movements
Maintenance of tissue homeostasis in multicellular organisms.
Sensory messages/reactions
Enables for humans to move to warmer place in times of coldness
There are receptors in the skin, sense organs (eyes, mouth, nose, and ears), and skeletal muscles which are able to detect changes in the environment, such as temperature, light, or texture
The autonomic nervous system: Contraction of the Heart, not controllable
Controls involuntary functions, such as heart rate,
respiration, stomach, endocrine glands, pupil
dilation
Can control skeletal muscles if rapid response is required (reflex arc).
Maintains homeostasis while the body is at rest or in an emergency
Regulates heart rate, blood pressure, body temperature, sweating and digestion.
Controls cardiac and smooth muscle, as well as glandular tissue
- Compare the sympathetic and parasympathetic nervous system.
Both are apart of the autonomic nervous system
Sympathetic- fight or flight, high sharp bursts of energy required (dialate pupils, increase heartbeat, inhibit stomach activity)
Parasympathetic-rest and digest
-controls basic bodily functions in a low stress environment (reading a book)
(constrict pupils, slow heartbeat, stimulate activity of the stomach)
ontrols basic bodily functions while one is sitting quietly reading a book.
- Draw and describe different types of neurons.
Nerve cell=neuron
A group of nerve cells make a nerve
What are the three types of nerve cells
AND
What are the 2 parts of a nerve cell u should look at t classify it
Sensory neuron
Interneuron
Motor neuron
Presence of Myelin Sheath
Where is the cell body located?
- Describe the structures and functions of the human eye as an example of the reflex arc.
Human reflexes-rapid and automatic
The path taken by the nerve impulses in a reflex is called a reflex arc.
The stimulus (a pin in the paw) stimulates the pain receptors of the skin, which initiate an impulse in a sensory neuron. This travels to the spinal cord where it passes, by means of a synapse, to a connecting neuron called the relay neuron situated in the spinal cord. The relay neuron in turn makes a synapse with one or more motor neurons that transmit the impulse to the muscles of the limb causing them to contract and remove the paw from the sharp object.
The iris reflex or person blinking when fly comes toward eye
iris contracting to prevent damage of the retina
The optic nerve is the main nerve that carries information to the CNS from the eye
- Describe the process of action potential.
Draw Diagram
An action potential is a rapid sequence of changes in the voltage across a membrane.
- Nerves are initially active and polarised
- At this point, it is resting potential, positive on outside, negative on inside.
- Sodium potassium pump is working (a pump on the surface of axons) Pump moves 3 sodium ions (Na +) out of the cell and 2 x potassium ions (k+) into the nerve
- This is distrupted by action (but continues through the process
- When a stimulus reaches a resting neuron- action potential
- Depolarisation- Sodium channels open, causing Na+ to enter the nerve. Therefore, the inside of the nerve becomes more positive. Resulting in depolarised. (sodium follows gradient into axon).
- This rush of sodium sends message down the nervous system
- At peak voltage, sodium channels close and potassium channels open (K+) moves out of nerve cell (repolarised)
- This reached hyperpolarization (opposite to polarisation) (sodium and potassium are wrong way)
- Sodium channels close , the sodium potassium pump returns the ions to the resting potential. To get back to normal.
When potassium channels open, the second nerve cells
- Define the term “threshold” and explain the all or nothing principle.
-threshold must be reached to ensure that the body doesn’t react unneccesarily to stimulus such as wind
All or nothing: reaction has to be over -55 volts in order for depolorisation to occur
Describe synaptic transmission by neurotransmitters and signal transduction.
There is space between each nerve cell- Synapse
This occurs at any point where 2 nerve cells are connecting Sensory, interneuron and motor neuron.
- Electrical impulse reaches the axon terminals of nerve cell 1
- Causes calcium channels to open, resulting in calcium being brought into the axon terminal
- Calcium causes vesicles (containing neurotransmitters) to fuse with the membrane, releasing the neurotransmitters to the synaptic cleft.
- Receptors on the dendrite of nerve cell 2 bind to neurotransmitter
- Sodium channels open and sodium is released into nerve cell 2, triggering the impulse in nerve cell 2
- Then, the neurotransmitter is recycled or destroyed by body
- Outline and explain the importance of the endocrine system in animals.
What is the endocrine system?
Uses chemical signals called hormones
to send messages around the body
These chemicals are produced in special
structures called endocrine glands in
response to a signal
Hormones are released into the
bloodstream and can travel to all parts
of the body
They only act on their ‘target cells’ (cells with the correct receptors can take the hormones in
The endorcirne system is a fundamental element of homeostasis. (glans releasing hormones when change of internal state is detected)
- Compare the role and response of the endocrine and nervous system.
Identify some of the glands and hormones involved in the endocrine system (pancreas, thyroid,
ovaries and testes and their hormones)
Pancreas Gland-
Located below the stomach
Produces hormones insulin and glucagon
Insulin reduces blood glucose levels (needed after eating)
Glucagon increases blood glucose levels (needed when hungry)
Thyroid Gland:
Located in the neck below the larynx
Produces thyroxine
Thyroxine controls the bodies metabolism
Gonad Glands: testes and ovaries
Ovaries
Testes releases androgens including testosterone
Androgens result in male sex characteristics
Ovaries produce oestrogen and progesterone
Results in female sex characteristics and regulates the menstrual cycle
Identify some of the glands and hormones involved in the endocrine system (pancreas, thyroid,
ovaries and testes and their hormones)
pancreas-
Thyroid Gland:
Located in the neck below the larynx
Produces thyroxine
Thyroxine controls the bodies metabolism
ovaries
testes and their hormones
- Describe the key role of the pituitary gland in mammals.
The hypothalamus is located in the base of the brain (so it is well protected)
It regulates basic functions including body temperature, water balance and heart rate
Pituitary gland is connected to the hypothalamus and is located just underneath
Pituitary gland has two lobes (posterior and anterior)
The Pituitary gland is considered to be the ‘master gland because it controls the function of other glands
Distinguish between posterior and anterior gland
Anterior
connected to hypothalamus by blood vessels
produces hormones based on signals that
come from the hypothalamus
Posterior
connected to hypothalamus by nerve fibres
not a true endocrine gland, as it does not make
any hormones.
Some hormones produced
by the hypothalamus pass down the nerve
fibre to the posterior pituitary gland and are
then secreted.
Homeostasis feedback loop: blood sugar levels
Describe/ draw feedback loop when blood glucose levels are too high
Stimulus-response system that maintains the body’s blood sugar levels within narrow limits
Too High:
Stimulus: blood sugar levels high
Receptor: Receptors on pancreas, (chemoreceptor)
Processing Centre: Endocrine System
Effectors: Body cells and livers
Response: Body cells take glucose for increased cellular respiration
Liver converts excess glucose to glycogen to store it for later use (such as when glucose is too low)
Negative Feedback: Blood sugar decreases
Too low:
Stimulus: Blood glucose too low
Receptor: chemoreceptors on pancreas
Processing centre: Endocrine system
Effector: Liver
Response: liver converts glucagen back to glucose and releases into the blood stream
Negative Feedback Loop
Diabetes: When the pancreas endocrine gland system goes wrong
Type 1 diabetes:
* When the body does not produce the
right amount (or any) insulin
-Usually develops in childhood or
adolescence
Treatment: daily injections of insulin
Type 2
he pancreas produces insulin but
cells stop responding properly to
insulin
* Usually develops in older people
* May need oral drugs or insulin
injections to treat, but can also be
controlled by diet and exercise
Hyperglycaemia:
* Blood glucose is above normal
* Can lead to damage to cells, heart
attack or strokes
* Treat by administering insulin
Hypoglycaemia
* Blood glucose is below normal
* Can lead to confusion and loss of
consciousness
* Treat by giving glucose
- Define endotherm and ectotherm and recall an example of each type of animal.
An ectotherm (reptile/amphibian) relies primarily on its external environment to regulate the temperature of its body. Cold blooded. Have fluctuating body temperatures
Endotherms (birds, humans, mammals) are able to regulate their body temperatures by producing heat within the body. Have stable body core temp.
- Describe how endothermic organisms maintain homeostasis.
Endotherms use internally generated heat to maintain body temperature.
Use metabolic heat
Behavioural, structural and physiological adaptations
Numerous mechanisms and/or organs may be activated to warm up or cool
down the body
What is radiation, conduction and convention? (thermoregulation)
-Conduction
-heat moves to a cooler area via touch
-sitting on cold metal bench and bench gains heat
Convection:
-movement of heat away from source via airflow
-windy days are cooler than still days
Radiation:
-natural slow movement of heat away from a source
-body naturally cools down by releasing heat in a cooler room.
