The nervous system

Brain + spinal cord.

2 main funcitons - control of behaviour + regulation of body's psych processes. To do this, brain must be able to receive info from sensory receptors + be able to send messages to muscles + glands - involves spinal cord (collections of nerce cells attached to brain + run length of spinal column).

Main function to relay info b/ween brain + rest of body. Allows brain to moniter + regulate bodily processes eg digestion + breathing, + co-ordinate voluntary movements.

Connected to diff parts of body by pairs of spinal nerves - connect w/ specific muscles + glands.

Also contains circuits of nerve cells - enable us to perform simple reflexes w/o direct involvement of brain.

If damaged, areas supplied by spinal nerves below damaged site cut off from brain - stop functioning.

Divided into 4 main areas - cerebrum, cerebellum, diencephalon + brain stem.

Cerebrum - largest part, 4 diff lobes w/ primary funcitons. Frontal love - thought + production of speech, occipital lobe - processing of visual images, the 2 hemipsheres - specialised for particular behaviours + communicate through corpus callosum.

Cerebellum - beneath back of cerebrum. Involved in controlling motor skills + balance, coordinating muscles to allow precise movements. Abnormalities can result in problems eg speech therapy, motor problems + epilepsy.

Diencephalon - beneath cerebrum, on top of brain stem. 2 structures - thalamus + hypothalamus. Thalamus - relay station for nerve impulses from senses, routing from appropriate part of brain where can be processes. Hypothalamus - regulation of body temp, hunger + thirst. Act as link b/ween endocrine + nervous system, controls release of hormones from pituitary gland.

Brain stem - regulates automatic functions essential for life eg breathing. Motory + sensory neurons travel through brain stemp, allows impulses to pass b/ween brain + spinal cord.

All nerves outside CNS. Function to relay nerve impulses from CNS to rest of body + from body back to CNS.

2 main divisions - somatic nervous system + autonomic nervous system.

Made up of 12 pairs cranial nerves + 31 pairs spinal nerves. Nerves have sensory + motor neurons.

Sensory neurons relay messages to CNS, + motor neurons relay info from CNS to other areas of body. 

Also involved in reflex actions w/o involvement of CNS, allows reflex to occur quickly.

Regulates involuntary actions. System necessary b/c vital bodily functions eg heartbeat wouldn't work as efficiently if had to think about them.

2 parts: sympathetic nervous system (SNS) + parasympathetic nervous system (PNS). Both of divisions tend to regulate same organs but have opp effects b/c of neurotransmitters associated w/ each division. 

Sympathetic division uses noradrenaline - stimulating effects.
Parasympathetic division uses acetylcholine - inhibiting effects.

Mainly involved in responses that help us deal w/ emergencies (fight/flight) eg increasing heart rate. Neurons from SNS travel to almsot every organ + gland w/in body, preparing body for rapid action necessary when under threat.

Causes body to release stored energy, pupils to dilate + hair to stand on end. Slows down bodily processes less important in emergencies eg digestion + urination.

Relaxes person once emergency passed. Slows down heartbeat, reduces blood pressure. Digestion begins again. Sometimes referred to as body's rest + digest system.