THE NERVOUS SYSTEM
Irritability-ability of body to respond to stimuli (a characteristic of a living organism)
Nervous system can communicate and coordinate different events of the body
3 sub-systems:-1the Central Nervous System-brain + spinal cord
2the Peripheral Nervous System-spinal nerves, cranial nerves + sense organs
3the Autonomic Nervous System-(para)sympathetic + nervous systems, control involuntary actions

The Central Nervous System
The Brain
located in the cranium part of skull, enclosed by meninges=3 membranes which enclose cerebrospinal fluid = lubricant and provides nutrients to brain cells
inside-white matter (nerve fibres=axons) outside -gray matter (cell bodies of neurones)
3 distinct regions:- 1fore brain, 2mid brain, 3hind brain
Fore brain
Cerebrum:-largest part of brain, made of 2 hemispheres, different parts > different functions (speech, motor, vision,etc.)
-concerned with intelligence, memory, learning, emotions, overall control of all voluntary actions
-larger surface area> more nerve cells > more intelligent
Hypothalamus:-concerned w/ regulation of body temp. + osmoregulation, 'thermostat' of body
Pituitary gland:-small pea-like structure attached to hypothalamus. master endocrine gland; controls endocrine glands

Mid Brain:- strip of brain located between fore and hind brain, concerned with visual reflexes for movement of eyeballs

Hind Brain
Cerebellum:-large and has a folded surface, concerned with muscle coordination and maintaining body balance
Medulla oblongata:-knob-like structure, below cerebellum, controls involuntary actions (heart beat, peristalsis)
Spinal cord:-continuation of MO, runs through neural canals of vertebral column (well protected), controls reflex actions

Neurones
-unlike normal cells they have dendrons, dendrites + axons (nerve fibres)
-axons insulated by thick fatty myelin sheaths which are discontinuous > form nodes of Ranvier at intervals
3 neurones:-
1sensory/afferent neurones-located between (in) receptors and CNS, convey nerve impulses from receptors to CNS
2relay/intermediate neurones-located in gray matter of CNS, relay events between sensory and motor neurones
3motor/efferent neurones-located between (in) CNS and effectors(muscles/glands), carry nerve impulses (for action)
impulse >receptors >sensory neurone >CNS >relay neurones >CNS >motor neurones >effectors >action

Spinal Cord
-continuous elongation of medulla oblongata, runs through neural canals of vertebrae of vertebral column (protected)
outside-white matter, inside-gray matter, enclosed by meninges containing cerebrospinal fluid
-has 2 equal halves, each with a dorsal and ventral root. sensory neurones-dorsal root, motor neurones-ventral root, relay neurones-gray matter. dorsal root-swellings = dorsal root ganglions; contain cell bodies of sensory neurones
-synapse = minute gap between dendrites of adjacent neurones, filled with chemical transmitters (eg. actylcholine + noradrenaline) nerve impulses carried by neurones, but at synapse by chemical transmitters

Reflex Actions
-spinal cord = seat of controlling all reflex actions except certain others controlled by brain
Reflex action = immediate response to an external stimulus w/o prior planning.
Divided into:1spinal reflex- controlled by spinal cord
2cranial reflex-controlled by brain (usually in head region: pupil reflex, salivation, blinking of eyes)
or
1simple:-takes place with reference to a stimulus, brain & spinal cord may be involved (involves reflex arc : pathway
through which nerve impulses are contacted: receptors>sensory neu.>CNS >relay neu.>CNS >motor neu.>effectors)
2conditional:-acquired from past exp. + learning,
stimulus at 1st = ineffective, due to continuous learning + exp. > more effective (salivation, swimming, typing)


Chemical Control of Plant Growth
The Use and Abuse of Drugs
Diversity of Organisms
Nutrient cycles and Ecology
Parasitism
The Human Impact on the Environment
Reproduction in plants
Sexual reproduction in animals
Genetics
Cell Structure and Organisation
Enzymes
Nutrition
Transport in Plants
Support, Movement and Locomotion
Transport system in man-circulatory system
Respiration
Excretion
Homeostasis
The Eye

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