- this is the largest part of the brain
- it is divided into two cerebral hemispheres, left and right
- these are joined by corpus callosum
- the outermost layer has a surface area of 2.5m^2 and it is folded
- it consists of a thin layer of nerve cell bodies known as cerebral cortex
- this area is highly developed in humans than in any other orgnisms
- The cerebrum contols the higher brain functions such as
- concious thoughts and emotional responses
- the ability to override some reflexes
- features associated with intelligence, such as reasoning and judgement
- Two areas of the brain (most found in the left cerebral hemisphere) are associated with understanding language and speaking
- these a Broca's area and Wernicke's area. Damage to these cause problems with understanding language.
- damage to Bronca's area will result with an inability to speak
- damage to Wenicke's area causes trouble understanding language.
- they are connected by a bundle of neurones
- if broke - unable to speak but understand the language
- visual sensory and association - Wernicke's area
- hearing sensory area - Broca's area
The cerebellum - movement and postures
- the concious decision to move voluntary muscle is initiated by the cerebral hemispheres
- the fine control of muscular movements requires a significant level of non-concious operation and involves the cerebellum e.g. walking and riding a bike
- examples - responding to changes in the body position to remain balanced and upright
- judging the position of objects and limbs
- tensioning of muscles in order to manipulate tools effectively
- feedback information on muscle position, tension and fine movement
- Neurones in cerebellum carry impulses to the motor areas so that motor output the effectors can be adjusted appropriately
- often feels like we are on 'auto-pilot' some activties become programmed into the cerebellum e.g. catching a ball
- the cerebellum contains over half of the nerve cells in the brain
Key role in balance and fine movement
- the cerebellum processes sensory information from
- the retina
- balance organs in the inner ear
- joints
- specialised fires in muscles called spindle fibres which relay information about muscle tension
Hypothalamus
- controls the body's homoeostatic mechanisms
- temperature regulations - input from thermoreceptors
- osmoregulation - input from osmoreceptors
- controls much of the endocrine function because it regulates pituitary gland
Medulla oblongata
- controls non-skeletal muscle eg. cardiac muscle, smooth muscle of the gut
- effectively in control of autonomic nervous system
- contains regulatory centres such as cardiac centre and the respiratory centre
- contains reflex centres for vomiting, coughing sneezing and swallowing
RESPONDING TO THE ENVIRONMENT
- The CNS (central nervous system) is a way of connecting sensors with effectors
- this is significant if living things are to escape predation, control balance and regulate temperature
- the nervous system is made up of the CNS and peripheral nervous system
CNS
- the central nervous system is made up of the brain and spinal cord
- it is made up of grey matter and white matter
- grey matter has billions on non-myelinated nerve cells
- white matter has longer, myelinated axons and dendrons
Peripheral nervous system
- relays impulses from sensors to the CNS
- it then relays impulses from CNS to effectors (motor neurones)
- this peripheral nervous system is divided into sensory and motor systems
Motor system
- the motor system is divided into
- somatic motor neurones - impulses from the CNS to skeletal muscle which are under voluntary concious control
- autonomic motor neurones - impulses from the CNS to cardiac muscle, smooth muscle in the gut to glands, involuntary (subconscious) control
Somatic v Autonomic
- Autonomic neurones are non-myelinated
- Somatic neurones are myelinated
- Autonomic connections to effectors consists of two neurones (connect at a ganglion)
- somatic connections to effectors consist of one
- autonomic
- independent of concious control
- controles homoeostatic mechanisms
- autonomic motor neurones occur in 2 types
- sympathetic
- dilates pupils
- no effects on tears glands
- accelerates heart, constrict arterioles
- dilates bronchi
- relaxes bladder
- most active in times of stress
- the neurones of a pathway are linked at a ganglion just outside the spinal cord. pre-ganglionic neurones are very short
- post-gaglionic neurones secrete noradrenaline t the end of the synapse etween neurone and effector
- parasympathetic
- constricts pupil
- stimulates tear glands
- inhibits heart, dilates arterioles
- constricts bronchi
- contracts bladder
- most active in sleep and relaxation
- the neurones of a pathway are linked at a ganglion within the target tissue. pre-ganglionic neurones carry considerable in length
- post-ganglionic neurones secrete acetyl-choline at the synapses between neurone and effector
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