A colourful and comprehensive, summary of the Human Nervous System, as covered in grade 12 Life Sciences (Biology).
Typed notes with thorough explanations using bullet points, pictures/labelled diagrams and tables - adapted from textbooks and class notes.
Concise, eye-catching and clear - the ul...
1. Nervous Tissue
2. Structure of the Human Nervous System (Central and
Autonomic Nervous Systems)
3. The effects of certain drugs on the Central Nervous System
4. Diseases of the Central Nervous System
5. Receptors (the eye and the ear)
1. Nervous Tissue
● The Human Nervous System enables humans to react to external &
internal stimuli in a coordinated way
● Consists of the Central Nervous System (CNS) – brain & spinal cord and
the Peripheral Nervous System (PNS) – Nerves that conduct nerve
impulses to and from the brain, via the spinal cord
● Made up of Neurons and Neuroglia (supporting tissue)
● Neuron/Nerve cell = basic unit of nervous system
● Neuron consists of:
● A cell body
● One or more dendrites
● One Axon
Neurons are classified according to their structure or function (There are three
types)
Functions Structure
1. Sensory/Afferent Neuron 1. Unipolar/Monopolar Neuron
- Transmit impulses from receptors to the CNS -1 Outgrowth that branches into 2 (1
- 1 Branch, 1 Dendrite & 1 Axon dendrite and 1 Axon)
- Unipolar/Bipolar
2. Motor/Efferent Neuron 2. Multipolar Neuron
-Transmits impulses from CNS to the effectors
-Cell body, many dendrites & 1 Axon
,-Multipolar -Many outgrowths, a number of dendrites
and 1 Axon
3. Interneuron 3. Bipolar Neuron (*Receptors)
-Found within CNS connects sensory & motor -2 Outgrowths (a dendrite and axon)
neurons
-Multipolar
Cell body = cytoplasm (Nissl granules: groups of ribosomes, rich in RNA –
protein synthesis) and nucleus
Dendrites = conduct nerve impulses toward the cell body.
Axon = conducts nerve impulse away from the cell body.
Schwann Cells = specialised cells that wrap around the axon, containing a
fatty protein (Myelin)
Myelin Sheath for insulates nerves and accelerates nerve impulses
Neurilemma = membrane surrounding the Myelin Sheath, repair/regeneration
of damaged nerves
Node of Ranvier = gaps, accelerate the impulse (jumps from one node to the
other)
Terminal Branches = conducts impulse from axon to synaptic knob
Synaptic Knob = secretes neurotransmitter (Acetylcholine) carries impulse to
next neuron
,The Structure and Functioning of Nerves
● Epineurium = layer of connective tissue which
surrounds nerve
● Bundles of neurons
● Each bundle surrounded by Perineurium
● Neurons surrounded by Endoneurium
● Transmission of Nerve Impulses:
● Travels as electrical signal through
dendrite, along axon to synaptic knob
● Synapse = gap between adjacent neurons
(*DO NOT TOUCH)
● How Impulses cross the synapse:
● Electrical impulse reaches terminal knob at end of axon
● Vesicles produce & secrete neurotransmitters
● Neurotransmitters diffuse across synapse
● Neurotransmitters attach themselves to dendrite of next
neuron
● New electric impulse travels along dendrite
● Why is a synapse NB?
● Ensures impulse travels in one direction
● Nerve impulse can be accelerated, decelerated or blocked
along its path
● *Body does it naturally or by using drugs
2. Structure of the Human Nervous System
, Central Nervous System
● Made up of the brain and spinal cord
● Protected by the vertebral column and cranium
● 3 Meninges (*PAD):
○ Pia Mater:
■ Innermost membrane
■ Rich blood supply = nourishes cells
○ Arachnoid Mater:
■ Loose membrane
■ Surrounded by cerebrospinal fluid i n the in the Subarachnoid
space
■ Cerebrospinal fluid: shock absorber, protects CNS from drying
out, maintains constant pressure around CNS, nourishes
nerve cells & removes waste
○ Dura mater:
■ Outermost membrane lines cranium and vertebral column
■ Tough and “Durable” for good protection
The Human Brain
● Top of spinal cord
● Grey & white matter
● Grey matter = outer layer (mostly cell bodies of neurons)
● White matter = inner section (mostly axons covered with fatty myelin
sheath)
● Ventricles = spaces in brain filled with cerebrospinal fluid
● 4 Main parts:
○ Cerebrum
○ Cerebellum
○ Hypothalamus
○ Medulla oblongata
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