The Brain and Nervous System

Cerebrum - control and information processing centre

• controls concious thought and emotional response
• can override some reflexes
• controls intelligence, reasoning and judgement

Cerebellum - controls coordiantion of movement/posture

Medulla Oblongata

• controls non-skeletal muscle
• controls the autonomic nervous system 
• the cente for respiratory and cardiac control

Hypothalamus - controls the homeostatic mechanisms and endocrine funtion of the body

...the largest part of the brain - divided into two hemispheres connected by the corpus callosum

The outermost layer is folded and a thin layer of nerve cell bodies - Cerebral cortex

The cortex is subdivided into areas:

• Sensory Areas - recieves impluses indirectly from receptors
• Association Areas - compare input with previous experiences in order to interpret what the input means and judge an appropriate response 
• Motor Areas - sends impulses to effectors

...the fine control of muscular movements such as those involved in walking, riding a bicycle, driving a car and playing musical instruments requires a significant level of nonconscious operation

impulses are carried from the cerebellum to the motor areas by neurones so that the effectors can be adjusted appropraitely - carrying out such activities as they becomes programmed into the cerebellum

it processes sensory information for balance and fine movement

...consists of the brain and spinal cord - it is made up of grey matter (non myelinated nerve cells) and white matter (longer, myelinated axons and dendrons that carry impulses)...

...made up of neurones that carry impulses into and out of the CNS

• Sensory Neurones carry impluses from the receptors around the body to the CNS 
• Motor neurones carry impulses from the CNS to the effectors 

Neurones are bundled together and covered in connective tissue and then subdivided:

• Somatic Motor neurones carry impulses form the CNS to skeletal muscles which are under voluntary control
• Autonomic Motor neurones carry impulses from the CNs to cardiac muscle/smooth muscle inthe gut/glands - none under voluntary control

...controls the majority homeostatic mechanisms - vital in regulating the internal environment of the body.

...capable of the controlling of the heightened response of the stress response

Organisation:

• most neurones are non-myelinated
• Neurones connect at a ganglion
• there are two types - sympathetic and parasympathetic

- antagonistic systmes becuase the action of one opposes the action of the other..

Under normal, resting conditions, impulses are passing neurones of both systems at a low rate. Changes to internal conditions or stimulation of the stress response, lead to an altered balance of stimulation between the systems, which leads to an appropriate response.

The balance of stimulation is controlled by subconcious parts of brain

• Most active during sleep and relaxation
• The neurones of a pathway are linked at a panglion within the target issue - pre ganglionic neurones vary in length
• Post-ganglionic neurones secrete acetylcholine as the neurotransmitter at the synapse between neurone and effector
• Effects of action:- decreased heart rate, pupil constriction, decreased ventilation rate,sexual arosal

• Most active in times of stress
• The neurones of a pathway are linked at a ganglion outside the spinal cord so pre-ganglionic neurones are very short
• Post-ganglionic neurones secrete noradrenaline at the synpase between neurone and effector
• Effects of action: increased heart rate, pupil dilation, increased ventilation rate and ******