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The Nervous System
Life Science
FLSS
All images used are taken from copyright-free sources e.g. Wikicommons Media or produced by UWS staff.
Internal communication - reminder
NERVOUS
ENDOCRINE
fast
slower, but more
sustained
mostly electrical
chemical
“hard wired”
more diffuse
Communication and Control
Nervous system – RAPID response to changes in internal
and external environment to maintain homeostasis
• Consists of
– Brain
– Spinal cord
– Peripheral nerves
• Communicates messages
– Partly electrically
– Partly chemically
• Cell types:
– Neurone - ‘business cell’
– Neuroglia - ‘supporting cell
’
Central Nervous System
(CNS)
Vs
Peripheral Nervous System
(PNS)
OpenStax College (2013)
http://commons.wikimedia.org/wiki/File:1201_Overview_of_Nervous_System.jpg
divisions of the nervous system
nervous system
central nervous system
brain
spinal cord
peripheral nervous
system
sensory
(afferent)
motor
(efferent)
somatic
(voluntary)
autonomic
(involuntary)
sympathetic
parasympathetic
UWS staff (2015)
summary of functioning of nervous system
Sensory input
Integration
(brain & spinal cord)
Motor output
ClipArt & UWS staff (2015)
Neurone
Lipothymia (2005)
https://commons.wikimedia.org/wiki/File:Neuron.jpg
http://training.seer.cancer.gov/module_bbt/unit02_sec04_b_cells.html
Neurone
• Cell body
– Contains nucleus and other cell structures
• Dendrite
– Conveys information towards the cell body
• Axon
– Conveys information away from cell body
• Nerve terminal
– Sends messages to next cell
Neurones
•
•
•
•
Information travels in one direction
dendrites  cell body  axon  terminal
Grey matter - cell bodies
White matter - axons & dendrites
• Nerve impulse (Action potential) - electrical signalling along
neurone
• Always > one neurone involved in nerve impulse
transmission
• No physical contact between neurones
• Electrical signal converted to chemical signal at synapse
Synapses
• Synapse - short gap between neurones
• When the nerve impulse (AP) arrives at
the synapse it causes release of
chemicals called neurotransmitters
from vesicles
• Neurotransmitters bind to receptors in
the postsynaptic cell
Synapses
Edk006 (2011) Neuronal Synapse. Available:
https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Neuronal_Synapse.jpg/800pxNeuronal_Synapse.jpg
US National Institutes of Health (2009)
https://commons.wikimedia.org/wiki/File:Chemical_synapse_schema_cropped.jpg
Synapses
• Postsynaptic cell can be
– Another neurone
– Muscle
– Gland
• Effect on postsynaptic cell can be
– Excitatory (‘on’)
– Inhibitory (‘off’)
• Neurotransmitters removed from synaptic cleft
either by:
– enzyme breakdown
– transport back into pre-synaptic neurone
Nervous System
• central nervous system (CNS)
– brain
– spinal cord
• peripheral nervous system (PNS)
– sensory (afferent)
– motor (efferent)
OpenStax College (2013)
http://commons.wikimedia.org/wiki/File:1201_Overview_of_Nervous_System.jpg
Peripheral nervous system
UWS Staff (2015)
Motor (efferent) nerves
• Somatic (voluntary) - movement of
voluntary muscles
• Autonomic (involuntary) functioning of smooth & cardiac muscle
& glands
– sympathetic
– parasympathetic
Autonomic nervous system
• The part of NS controlling automatic
body functions; it regulates:
• Involuntary Muscles
– in the skin (around hair follicles; smooth
muscle)
– around blood vessels (smooth muscle)
– in the eye (the iris; smooth muscle)
– in the stomach, intestines and bladder
(smooth muscle)
– of the heart (cardiac muscle)
• Glands
Autonomic nervous system
• The ANS controls 2 situations:
– emergency situations that cause
stress and require us to
‘fight’ or take ‘flight’ (run away)
– non-emergency situations that
allow us to ‘rest’ and ‘digest’
Autonomic nervous system
• Sympathetic division
– “fight or flight” (responses to stress)
– energy expenditure
Threatening situation: Sympathetic nervous system increases
heart rate and respiration
• Parasympathetic division
– Conserving energy
Relaxing situation: Parasympathetic NS increases digestion
Most organs controlled by both, two divisions have
opposite (antagonistic) effects
Autonomic nervous system
BruceBlaus. (2013)
https://commons.wikimedia.org/wiki/File:Blausen_0838_Sympathetic_Innervation.png
BruceBlaus. (2013)
https://commons.wikimedia.org/wiki/File:Blausen_0703_Parasympathetic_Innervation.png
The Brain
• Cerebrum
• Cerebellum
• Brainstem
John A Beal (2005)
https://commons.wikimedia.org/wiki/File:Human_brain_midsagittal_cut_color2.png
Cerebrum
• Largest part
• Receives sensory info.
• Initiates/controls muscle contractions
(voluntary movement)
• Site of higher functions
–
–
–
–
Processing info
Understanding
Thinking/memory
‘personality’
Sensory Cortex
OpenStax College (2013)
http://commons.wikimedia.org/wiki/File:1421_Sensory_Homunculus.jpg?uselang=en-gb
Cerebellum
• Co-ordinates
–Voluntary movement
–Posture
–balance
Brain stem
• Contains vital centres controlling
– Breathing
– Heart beat
• Relay between spinal cord and higher
brain
• Important in consciousness and
alertness
Spinal cord
• Carries info. from body to brain
– ascending
– sensory
– afferent
• Carries info. from brain to body
– descending
– motor
– efferent
• Responsible for reflex actions
CNS protected by
• Bone
– skull & vertebrae
• Meninges
– 3 membranous layers between
– Skull and brain
– Vertebrae and spinal cord
• Cerebrospinal fluid (CSF)
– between brain / meninges /spinal cord
– brain ventricles,
– central canal of spinal cord
Protection of CNS
bone
• skull & vertebrae
meninges (membranes)
• dura mater (epidural
anaesthetic
epidural space)
• arachnoid
• pia mater
into
WikiFB3 (2007) Hersenvliezen. Available:
https://upload.wikimedia.org/wikipedia/commons/d/db/Hersenvliezen.jpg
Korribot (2009) http://commons.wikimedia.org/wiki/File:Meninges_diagram.jpg
•
•
•
•
•
Withdrawal reflex
Patellar reflex
Plantar flexion reflex
Eye blink reflex
Pupillary reflex.
Ruth Lawson Otago Polytechnic (2007) Anatomy and physiology of animals Relation btw sensory, relay &
motor neurons. Available:
http://commons.wikimedia.org/wiki/File:Anatomy_and_physiology_of_animals_Relation_btw_sensory,_
relay_%26_motor_neurons.jpg
Reflexes