14. Coordination and Response Flashcards
(29 cards)
Describe the mammalian nervous system
Mammalian nervous system consists of:
1. The central nervous system (CNS) consisting of the brain and the spinal cord
2. The peripheral nervous system (PNS) consisting of the nerves outside of the brain and spinal cord
Describe the role of the nervous system
Coordinate and regulate body functions. Allowing us to make sense of our surroundings and respond to them.
Describe a simple reflex arc
- The stimulus is detected: By a receptor in the skin
- Sensory neurone sends electrical impulses: To the spinal cord (the coordinator)
3, Electrical impulse is passed on: To relay neurone in the spinal cord - Relay neurone connects: To motor neurone and passes the impulse on
- Motor neurone carries impulse: To a muscle in the effector
- The muscle responses: By contracting and pulling the effector away from the stimulus object
Describe a reflex action
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)
Describe a synapse
Junction between two neurones
Describe the events at a synapse
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- Trigger: When an electrical impulse travels along the first axon, it stimulates the nerve-ending of the presynaptic neurone to release neurotransmitters from vesicles. These fuse with the presynaptic membrane and are released into the synaptic cleft.
- Diffusion: Neurotransmitter molecules diffuse across the synaptic cleft (gap).
- Binding: Upon reaching the postsynaptic membrane, neurotransmitters bind with the receptor proteins on it.
- Impulse: The binding stimulates the second neurone to generate an electrical impulse that travels down the second axon.
Describe sense organs
Groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
Describe the function of each part of the eye, limited to: cornea, iris, lens, retina, optic nerve
(a) cornea – refracts light
(b) iris – controls how much light enters the pupil
(c) lens – focuses light on to the retina
(d) retina – contains light receptors, some sensitive to light of different colours
(e) optic nerve – carries impulses to the brain
Explain the pupil reflex, limited to changes in light intensity and pupil diameter and in terms of the antagonistic action of circular and radial muscles in the iris
- In dim light: Light receptors in the eye detect low light intensity. To maximise light entering the eye, the pupil dilates. This is achieved by the contraction of radial muscles in the iris, while the circular muscles relax
- In bright light: Light receptors in the eye detect high light intensity. To reduce light entering the eye, and protect the retina, the pupil constricts. This is achieved by the contraction of circular muscles in the iris, while the radial muscles relax
Explain accommodation to view near and distant objects
- Near: Light needs to be refracted more. For this to happen, the ciliary muscles contract to loosen the suspensory ligaments. This exerts a less pull on the lens, allowing the lens to be more rounded
- Distant: Light needs to be refracted less. For this to happen, the suspensory ligaments tighten while the ciliary muscles relax. This action pulls on the lens, causing it to be thinner
Describe the distribution of rods and cones in the retina of a human
- Rod cells: All over the retina (except the blind spot)
- Cone cells: Concentrated in the fovea (where light is focused during accommodation)
Outline the function of rods and cones
- Rods: Greater sensitivity to detect light at low levels for night vision
- Cones: Three different kinds of cones which detect light at three different wavelengths. Absorbing light of different colours, for colour vision
Describe a hormone
A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
State the hormones secreted by the endocrine system
(a) adrenal glands and adrenaline
(b) pancreas and insulin
(c) testes and testosterone
(d) ovaries and oestrogen
Describe adrenaline
Hormone secreted in ‘fight or flight’ situations
Describe the effects of adrenaline
- Increased breathing rate and heart rate: Glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, from muscles cells more quickly
- Increased pupil diameter (dilates): To allow as much light as possible to reach the retina, so more information can be sent to the brain
Describe the role of adrenaline in the control of metabolic activity
- Increased blood glucose concentration: More important glucose is delivered to muscle cells for increased respiration
- Increased heart rate: Ensures all muscles are well prepared for high levels of activity in a flight or fight situation
Compare nervous and hormonal control, limited to speed of action and duration of effect
- Nervous control: Fast acting, short-lasting
- Hormonal control: Slow acting, long-lasting
Describe homeostasis
The maintenance of a constant internal environment
Explain the concept of homeostatic control by negative feedback with reference to a set point
- Concept of homeostatic control by negative feedback:
Negative feedback mechanisms is a continuous cycle of that brings levels of conditions up and down, to return the conditions to its set point after being changed from the ideal - So if the level of something rises, control systems are switched on to reduce it again. If the level of something falls, control systems are switched on to raise it again
Describe the control of blood glucose concentration by the liver and the roles of insulin and glucagon
- Blood glucose concentration is controlled by negative feedback mechanism involving the production of the hormones insulin and glucagon
- When blood glucose rises, insulin is produced to stimulate the liver and muscle cells to convert excess glucose into glycogen, for storage
- When blood glucose falls, glucagon is produced to stimulate the liver and muscle cells to convert stored glycogen into glucose, and release it into blood cells
Outline the treatment of Type 1 diabetes
- Blood glucose levels are too high, so extra insulin is injected. Causing the liver to convert glucose into glycogen, reducing the blood glucose level.
- To help control the level, patients can exercise (lowers blood glucose level through increased respiration in the muscles) or be careful with their diet (not eating foods that’ll spike blood glucose level)
- Symptoms include: Extreme thirst, weakness or tiredness, blurred vision, weight loss and loss of consciousness
Describe the maintenance of a constant internal body temperature in mammals in terms of: insulation, sweating, shivering and the role of the brain
- Brain receptors: Controls temperature regulation. As they’re sensitive to the temperature of the blood
- Thermoreceptors: In the skin, detects change in body temperature as the body shivers/sweats. Sending nervous impulses to the brain via sensory neurones
- Response: The brain sends nerves impulses to effectors in the skin, to maintain the temperature within a narrow range of the optimum, 37°C
- Fatty tissue: Under the dermis acts as a layer of insulation. Preventing a lot of body heat from being lost through the skin
Describe the maintenance of a constant internal body temperature in mammals in terms of vasodilation and vasoconstriction of arterioles supplying skin surface capillaries
a) Vasodilation: In hot situations, blood vessels to the skin capillaries get wider/dilates, causing blood flow in capillaries to increase. As a result, the body cools because blood (carries heat) is flowing at a faster rate through the skin’s surface, so more heat is lost by radiation
b) Vasoconstriction: In cold situations, arterioles leading to the skin capillaries get narrower/constricts, causing blood flow in capillaries to slow down. As a result, the amount of heat lost from blood by radiation reduces, as less blood flows through the surface of the skin
