B10 The nervous system, eye and brain
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What is homeostasis
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function
What 2 conditions need to be maintained for optimum enzyme action
pH Temperature
What is negative feedback
When a change away from the ideal triggers a reaction to bring the change back to normal
What 3 things need to be controlled by negative feedback
Water levels Body temperature Blood glucose concentration
What are receptors
Detect changes in the internal or external environment
What are stimuli
A change in the environment
What is an effector
A muscle of gland that brings out a response
What is a coordinator
Areas that receive and process information from receptors
Give 5 examples of coordinators in the body
Brain Pancreas Nervous system Endocrine system Spinal cord
Describe the function and structure of the sensory neurone
Connects the receptor to the CNS Has a nucleus Myelin sheath for insulation Has axon Cell body is in the middle
Describe the function and structure of the motor neurone
Connects CNS to muscles/glands Has a nucleus Myelin sheath for insulation Has axon Cell body is at the end
How does the body respond to a stimulus
The receptor cell detects the stimulus An electrical impulse is sent via nerves along the sensory neurone to the CNS The CNS coordinates the response An electrical impulse is sent along the motor neurone to a muscle or gland This triggers a response
What is the central nervous system made up of
Spinal chord and brain
What are the 4 sense organs and what receptors do they contain
Eyes-Light Ears-Sound, pressure Nose-Chemical(smell) Skin-Pain, pressure, change in temperature
Name 2 effectors and how they respond to impulses
Muscles-Contract Glands-Secrete hormones
What is the relay neurone
Connects sensory and motor neurone and is involved in a reflex action
What is a synapse
Junction between 2 neurones
How does a synapse work
The impulse arrives at the end of the axon Chemical messengers called neurotransmitters are released These chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the second neurone The binding of the neurotransmitter to the receptor stimulates the second neuron to transmit an electrical impulse
What is the function of the cerebral cortex
Concerned with consciousness, intelligence, memory and language
What is the function of the hypothalamus
Controlling body temperature
What is the function of the pituitary gland
Secretes hormones Produces chemicals
What is the function of the cerebellum
Coordinating muscular activity and balance
What is the function of the medulla
Unconscious activities such as controlling heartbeat, movement of gut and breathing
What is the function of the: Pupil Cornea Ciliary muscles Retina Blind spot Optic nerve Lens Iris
Pupil-Lets in light Cornea-Protects eye and refracts light Ciliary muscles-Changes the shape of the lens Retina-Contains light sensitive cells to detect image Blind spot-Where the optic nerve needs the retina Optic nerve-Sends electrical impulses to the brain Lens-Focuses objects Iris-Changes the shape of the pupil