Coordination and response Flashcards
Describe a reflex arc
Receptor detects stimulus …
Impulse moves along sensory neurone to central nervous system (relay neurone)
Neurotransmitters diffuse across synapse
Motor neurone to effector
Effector carries out response (muscle contraction)
What is the central nervous system?
Consists of the brain and spinal cord. Coordinates all responses (movement and reflexes). It is linked to sense organs by nerves.
Name the 3 different types of neurones and their purpose
Sensory neurones - carry impulses to central nervous system
Relay neurones - decreases response time between sensory and motor
Motor neurones - carry neurones away from central nervous system, to the effector
What is an effector?
Usually a muscle, carries out a response
What is a synapse?
A small gap between 2 neurones
Describe what happens at the synapse
Release of neurotransmitters
Diffuse across the gap (synapse)
Transmitting the impulse between neurones
Advantages of reflexes
Fast
No brain involvement/involuntary
Less damage/harm
How does the eye adjust to looking at a distant object?
Suspensory ligaments contract
Ciliary muscles relax
Lens becomes long and thin (less convex shape)
Less refraction of light
How does the eye adjust to looking at a close object?
Suspensory ligaments relax
Ciliary muscles contract
Lens becomes thicker with a more convex shape
More refraction of light
How does the eye adjust to bright light?
Circular muscles contract
Radial muscles relax
Iris becomes wider
Pupil constricts, letting less light in
How does the eye adjust to dim/no light?
Radial muscles contract
Circular muscles relax
Iris becomes narrower
Pupil dilates to let more light in
What happens if blood glucose is too high?
Pancreas produces the hormone insulin.
Insulin stimulates cells to take glucose in from the bloodstream (particularly from the liver and muscles cells)
In liver and muscle cells excess glucose is converted into glycogen for storage.
What happens if blood glucose is too low?
Pancreas produces the hormone glucagon.
Stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the bloodstream, increases the blood glucose levels.
How does the body respond when it is cold?
Piloerection - Hair stands on end. Warm air becomes trapped underneath the hairs, creating a convection current that acts as a warm insulating layer.
Vasoconstriction - Arterioles supplying the capillaries near the surface of the skin constrict (get narrower). Less blood flows near the surface of the skin so less heat is lost by radiation.
Less sweat released so less heat lost by evaporation.
How does the body respond when it is hot?
Pilorelaxation - Hairs lie flat and so an insulating layer of air isn’t formed. More heat is lost.
Vasodilation - Arterioles supplying the capillaries near the surface of the skin dilate. More blood flows near the surface of the skin, so more heat is lost by radiation.
More sweat is released - When sweat evaporates, heat energy is taken away from the skin as the evaporation of water requires energy.
How does fight or flight reflex occur in the body?
Blood diverted from intestine to muscles. Increased heart rate means more blood to muscles. Breathing rate increases/deeper breathing. Rate of respiration increases as more oxygen is delivered to muscle cells.
Pupils dilate - increased visual sensitivity.
Glycogen converted to glucose.
What is homeostasis?
The maintenance of a constant internal environment.
What is the source, role and effect of the hormone adrenaline?
Released by adrenal gland.
Increases heart and breathing rate for fight or flight response
What is the source, role and effect of the hormone insulin?
Released by pancreas.
Causes liver and muscle cells to take up glucose and convert it into glycogen for storage
What is the source, role and effect of the hormone testosterone?
Released by testes.
Causes development of male secondary sexual characteristics.
What is a tropism?
Directional growth responses made by plants in response to light or gravity (stimuli)
What is the difference between a positive and negative response?
Positive - growth towards the stimulus
Negative - growth away from stimulus
What are the words for responses to light and responses to gravity?
Light - phototropism
Gravity - geotropism
What would the responses for a plant growing towards light and upwards be?
Positive phototropic response - towards light
Negative geotropic response - away from gravity
What are auxins?
Plant growth regulators. They coordinate and control directional growth responses (phototropism and geotropism). Made in the tips of shoots. Cause cell elongation.
What happens when light is shone predominantly on one side of a plant?
Auxin produced in the tip concentrates on the shaded side, making the cells elongate and grow faster than the cells on the sunny side. Unequal growth causes the shoot to bend and grow in the direction of light.
What are the differences between nervous and hormonal communication control responses?
Nervous uses neurones, hormone uses plasma.
Nervous is electrical. Hormone is chemical.
Nervous goes to target/specific cells only. Hormone goes all around body/different organs.
Nervous response is usually short term. Hormone response is longer lasting
Describe the reflex arc of the withdrawal of a finger from a hot object
Receptors in skin detect stimulus
Impulse travels from sensory neurone to relay neurone via diffusion of neurotransmitters across the synapse
Motor neurone to muscle/effector
Muscle/effector contracts
Function of the cornea
Transparent front layer helps to focus light entering the eye.
Function of the lens
Adjust its shape to focus light precisely onto the retina.
Function of the retina
Contains rods and cells (photoreceptors) that detect light intensity and colour
Function of the optic nerve
Transmits visual information from the retina to the brain for interpretation.
Function of the iris
The coloured part of the eye that controls the size of the pupil, regulating the amount of light entering the eye.
