Coordination and Response

V bio test

How do organisms respond to changes in their environment?

* land animals survive by responding to changes in their surroundings
* there are many different stimuli, such as temperature which they respond to
* this is contolled by the nervous system

homeostasis

the maintenace of a constant internal environment e.g body water content + body temperature

coordinated response requires

* stimuli
* receptor
* effector

stimuli

change in the environment

receptor

* cells that detect change and send nerve impulses to the spinal chord
* found in sense organs

effector

* cells that coordinate a response to the stimuli
* found in muscles and glands

plants respond to many different stimuli

* direction of light - more photosynthesis
* gravity
* climbing plants have a sense of touch so they can find things to climb

stems experience

* positive phototropism
* negative geotropism

roots experience

* negative phototropism
* positive geotropism

positive phototropism

grow in the direction of sunlight

negative phototropism

grow away from sunlight

positive geotropism

grow in the direction of gravity

negative geotropism

grow in the opposite direction of gravity

auxin definition

a plant hormone produced in the tips of stems and roots which controls the direction of growth

role of of auxin in the phototropic response of stems

* auxin produced at the tip will be distributed by light receptors to the shaded side of the stem
* cells on the shaded side will grow larger and elongate, whilst cells on the side exposed to light will grow at a slower rate
* as a result the plant will grow towards the light

characteristics of the nervous system

• electrical impulses

• short lived and quick responses

• localised responses

• temporary

endocrine system

* chemicals
* longer lasting and takes much longer to travel
* widespread response
* permanent

central nervous system

* brain
* spinal chord

how is the CNS linked to the sense organs?

CNS is liked to the sense organs by nerves made up of neurones (nerve cells)

three types of neurones

* sensory neurones
* relay neurones
* motor neurones

has no involvement with the conscious part of the CNS

the reflex arc, this is why it is so fast and effective

reflex arc

* when a receptor detects a stimuli, electrical impulses are sent to the CNS along sensory neurones
* they then pass the impulse to the relay neurone, which pass it to a motor neurone
* they then pass it to the effector (muscle)
* the effector reacts and responds to the change

synapse

junction between two neurones

role of neurotransmitters at synapses

* when electrical impulses are at the end of a neurone, neuro transmitters are released
* they diffuse across the synapse and bind with the receptor moleucles of the second neurone
* this stimulates the electrical impulse to continue along the neurone

structure of a simple reflex arc - withdrawal of a finger from a hot object example

1. temperature receptors in the skin detect the hot object
2. electrical impulses are passed along to the CNS along the sensory neurones
3. electrical impulses are passed through the relay neurones and then through the motor neurones
4. the impulses will then travel from the motor neurone to an effector (muscle)
5. the muscle contracts and the hand moves away from the hot object

diagram of an eye

memorise

label this

functions of the iris

made of circular and radial muscles to control the amount of light entering

function of the lens

refracts light to create image on retina

function of the pupil

hole in the middle of the iris to let light through

function of the cornea

first lens, part of the sclera

conjunctiva

membrane covering the cornea, lines the eyelid

ciliary muscles

changes shape of the lens

chloroid

dark layer containing pigment cells, stops reflection

sclera

tough outer layer that protects the eye

retina

covered in light receptors called cones and rods, changes light into electric energy

fovea

dip in retina, concentration of cone cells

blind spot

area with no rod, cone cells, where the optic nerve leaves the retina

optic nerve

carries impulses from the receptors to the brain

eye focusing on far objects

* suspensory ligaments pulled tight
* lens pulled flat
* ciliary muscles relax
* less light refraction

eye focusing on near objects

* suspensory ligaments slacken
* lens is more rounded
* ciliray muscles contract
* more light refraction

eye focusing on bright light

* radial muscles relax
* circular muscles contract
* pupil is constricted (smaller)

eye focusing on dim light

* radial muscles contract
* circular muscles relax
* pupil is dilated (bigger)

vasoconstriction - when the body is cold

* blood vessels constrict
* blood flows through deeper vessels
* less heat is radiated

shivering

* hair erector muscles contract to trap insulating layer of air
* shivering increases rate of respiration which transfers more energy to warm the body

vasodilation

* blood vessels dilate
* blood flows through surface vessels
* more heat is radiated

sweating

* vasodilation occurs
* sweat glands produce sweat
* skin uses body heat to evporate
* hair erector muscles relax so hair lies flat

adrenaline (source, role, effects)

* source - adrenal glands
* role - readies body for ‘fight’ or ‘flight’ response
* effects - increase in heart rate and blood flow to the muscles

insulin (source, role, effects)

* source - pancreas
* role - controls blood sugar levels
* effects - stimulates the liver to turn glucose into glycogen

four hormones that control the menstrual cycle

oestrogen

progesterone

FSH

LH

oestrogen and progesterone role and source

maintaining the uterus lining

oestrogen produced by the ovaries

progesterone produced by the corpus luteum

FSH role and source

maturation of an egg in the ovary

stimulates the ovaries to start releasing oestrogen

pituitary gland

LH role and source

stimulates the release of the egg

stimulates the release of progesterone from the ovary

pituitary gland

testosterone source and role

produced in the male testes

responsible for the development of secondary sexual characteristics in males