topic 14: coordination and response

central nervous system (CNS)

consists of the brain and spinal cord, which are the areas of coordination

peripheral nervous system (PNS)

compromised of nerves and neurones that coordinate and regulate body functions

nerve impulse

an electrical signal that passes along the nerve cells called neurones

axons

ensures less time is wasted when the impulse is transferred from one neurone to another

dendrites

extensions which form a network for easy communication

sensory neurone

carry impulses from the sense organs (sensory receptors) to the CNS

relay neurone

the middleman inside the CNS connects sensory to motor neurones

motor neurones

carry impulses from the CNS to effectors (muscles, or the glands)

reflex action

automatically and rapidly integrates and coordinates the stimuli with the responses of effectors

synapse

a junction between two neurones, consisting of a gap across which impulses pass by diffusion of a neurotransmitter

synaptic cleft

the small gap between each pair of neurones

sense organs

group of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

cornea

refracts light

iris

controls how much light enters the pupil

lens

focuses light onto the retina

retina

contains light receptors, some sensitive to light of different colors

optic nerves

carry impulses to the brain

pupil

a hole which allows light to enter

low light intensity

radial muscles contract, circular muscles relax, pupil size widens, amount of light entering is more

high light intensity

radial muscles relax, circular muscles contract, pupil size narrows, amount of light entering is less

near object accommodation

ciliary muscles contract, suspensory ligaments slack and lens are short and fat

distant object accommodation

ciliary muscles relax, suspensory ligaments tighten, lens are long and thin

rods

suitable for seeing in low-intensity light and packed tightly around the edge of the retina

cones

work well in high light intensity, and mostly packed at the retina’s centre

fovea

part of the retina where the receptor cells are pushed most closely together

hormones

a chemical substance produced by a gland and carried by the blood, altering the activity of one or more specific target organs

adrenaline

adrenal gland, prepares body for vigorous action

insulin

pancreas, reduces the concentration of glucose in the blood

testosterone

testes, causes development of male sexual characteristics

oestrogen

ovary, causes the development of female sexual characteristics

glucagon

pancreas, increases concentration of glucose in the blood

homeostasis

the maintenance of a constant internal environment

negative feedback

controls the production of hormones and regulates their own production

diabetes

caused by the death of the cells that secrete insulin

symptoms of diabetes

dry mouth, blurred vision and feeling unwell

vasoconstriction

blood flow in the capillaries slows down because the arterioles leading to the skin capillaries get narrower when we are cold, less blood flows through so lesser heat is lost

vasodilation

blood flow in capillaries increase because blood vessels to the skin capillaries get wider when we are hot, cools the body as blood flows faster

auxin

it controls tropisms, produced by cells at the tip of roots and shoots of plants

gravitropism

a response in which a plant grows towards or away from gravity

auxins in gravitropism

auxins diffuse through the plant from the shoot tip, and is unequally distributed in response, stimulating cell elongation

auxins in phototropism

auxins accumalate to the side with no light, so that side’s cells grow faster, so that the shoot will bend to the sunlight

phototropism

a response in which a plant grows towards or away from the direction light is coming