B10: The human nervous system

Homeostatis

regulation of internal conditions to maintain optimal conditions, in response to internal/external changes

Examples of controlled internal conditions

body temperature, water content of body, blood glucose concentration

Receptors

cells that detect changes in the environment

Stimuli

changes in the environment (sg. stimulus)

Coordination centres

areas that receive and process the information and coordinate a response

Effectors

muscles or glands that bring about a response

Why is homeostasis important?

maintains optimum conditions for enzyme action and all cell functions

Automatic control systems may involve...

nervous of chemical responses

Nervous system

allows to react to surroundings and coordinate behaviour by using electrical impulses

Neurone

single nerve cell

Nerve

bundle of neurones

What is the central nervous system (CNS) made up of?

brain and spinal cord

Sensory neurones

cells that carry impulses from receptors to CNS

Motor neurones

cells that carry impulses from CNS to effector

Relay neurone

cells that carry impulses from the sensory neurones to the motor neurones, are found in CNS

Nervous system chain

stimulus -> receptor -> CNS -> effector -> response

Reflexes

automatic and rapid responses that do not involve the conscious part of your brain

Reflex arc

stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response

Synapses

connections between neurones

How are electrical impulses transmitted across synapses?

electrical signals are transferred by checmials which diffuse across the gap. chemicals then set off a new electrical signal in the next neurone.

Cerebral cortex

concerned with consciousness, intelligence, memory and language

Medulla

concerned with unconscious activities (eg. heartbeat, breathing, gut movement)

Cerebellum

concerned with coordinating muscular activity and balance

What (3) methods do scientists use to study the brain?

studying patients with brain damage, electrically stimulating the brain, MRI scans

Scelera

tough supporting wall of eye

Cornea

refracts light and let it into eye

Iris

controls size of pupil and amount of light entering eye

Lens

focuses light onto the retina

Ciliary muscles and suspensory ligaments

change shape of lens to fine focus light onto retina