Biol125 – Human Physiology
L1
Anatomical Terminology: e.g. in CT scanner
Brain/body viewed in 3 planes = sagittal, coronal, transverse
Superior= Above
Inferior = Below
Anterior or Ventral = Front
Posterior or Dorsal = Back
Medial = close to midline
Lateral = away from midline
Functions of Nervous System:
Central Nervous System (CNS) = brain + spinal cord
Peripheral Nervous System (PNS) = cranial + peripheral nerves
➔ Sensory function: detect external + internal changes e.g. breathing rate -> maintain
homeostasis
➔ Integrative function: analyses + makes decisions based on voluntary + involuntary responses
➔ Motor function: initiates motor movement + glandular secretions
Gross Anatomy of Brain:
• Cerebrum: largest part of brain -> contains cerebral cortex + subcortical regions
• Cerebellum: located in posterior region of brain, responsible for balance + coordination ->
allows learning
• Brainstem: contains midbrain, pons + medulla oblongata -> communicates with PNS ->
control involuntary processes such as breathing + heart rate
• Gyrus: ridges of cerebrum (gyri)
• Sulcus: grooves of cerebrum (sulci)
Cerebrum:
Contains cerebral cortex + subcortical regions
Corpus callosum: large fibre bundle connecting 2 hemispheres
Cerebral cortex: outermost layer of nerve tissue
4 functionally + anatomically distinct lobes:
1. Frontal lobe: higher cognitive functions = decision making, problem-
solving, responsible for some features of language + voluntary
movement
➔ What gives us identity/independence
2. Parietal lobe: integrates information from visual pathways, coordinates motor movement +
interpretation of sensory information
3. Temporal lobe: interpreting speech, hearing, object recognition + emotion
4. Occipital lobe: processing primary visual information e.g. Flips upside down image + sends it
to parietal lobe
Subcortical Regions:
,Subcortical = underneath cortex
The Limbic System: Responsible for functions that integrate information e.g. memory, emotions,
motor, movement, processing, sensory information
1. Hypothalamus: maintains homeostasis
2. Amygdala: emotional learning + behaviour
3. Hippocampus: memory (long-term) + spatial navigation
4. Thalamus: sensory + motor function
5. Basal ganglia: involuntary movements e.g. tremors, athetosis
Medulla + hippocampus interact -> remember strong emotions
Midbrain:
➔ Serves as connection between brainstem + subcortical
regions
Oldest part of brain in evolution
Pons: relay centre connecting different parts of brain e.g. forebrain
and cerebellum
Medulla oblongata: cardiac, respiratory, vomiting, vasomotor centres
➔ Involuntary control of breathing rate, heart rate, blood
pressure
1. Colliculi: directs eye movement towards objects of interest
2. Tegmentum: coordinates movement, sleep e.g. involved in Parkinson’s disease
3. Cerebral peduncle: involuntarily control of ocular muscles -> controls eye movement
Spinal cord:
➔ Links CNS + PNS
Nerves branching off from spinal cord -> form PNS + innervate the rest of the body
Innervate: supply organ/body part with nerves
Only have 1 spinal cord -> injury means all communication in between damage +
brain remains
5 Divisions based on corresponding body area that is innervated:
1. Cervical = supplies nerves to neck
2. Thoracic = supplies nerves to head
3. Lumbar = supplies nerves to lower back
4. Sacral = supplies nerves to hip
5. Coccygeal = supplies nerves to tail
,Peripheral Nervous System:
Sympathetic Nervous System: responsible for fight or flight reaction occurring in response to
stressful stimulus e.g. increase heart rate
Parasympathetic Nervous System: responsible for rest or digest = balances sympathetic nervous
system
Interactions between sympathetic + parasympathetic NS = crucial for maintaining homeostasis
Afferent pathways: carry sensory information from periphery up to the brain via ascending nerve
tracts
Nerves on left of body stimulate right of brain – come up dorsal spinal cord
Efferent pathways: brain send signals down to peripheral nerves along efferent descending nerve
tracts to control motor output – come down ventral part of spine
Reflex arc: all information stays in spine – doesn’t stimulate brain
1. Knee is hit
2. Sensory afferents in knee send information to dorsal column of spinal cord
3. Afferents synapse onto interneurons within spinal cord
4. Interneurons send signals to muscles of legs via efferents nerve originating in ventral horn
5. Efferent fibres communicate with muscles, causing them to contract + jerk leg
Pain is still transmitted to brain
Ventral horn/column: grey matter in anterior part of spinal cord, contains neurones
CNS Cells:
1. Neuron: specialised cells receive + send signals within CNS +
between CNS and PNS
1) Dendrites: finger like protrusions that receive input
from other cells
2) Information is relayed to cell body = soma
3) Axon: signal is sent down
4) Axon terminal: where chemicals (neurotransmitters)
are released onto another neurons at synapse
Long, thin, propagate nerve
Mylein sheath
Types of Neurones:
a. Bipolar neurone: 1 axon + 1 dendrite e.g. in retina, inner ear
b. Unipolar neurone: 1 process from cells body, part way down from axon
, Always sensory neurones e.g. pain, temperature
c. Multipolar neurone: many dendrites + 1 axon
Most popular – in CNS
2. Glial cells:
1) Microglia: immune cells survey CNS + respond to signals
of infection or damage
• Only glial cell to have axons
• Exist in wide range of morphologies depending
on activation site
Can be in surveillant or activated form:
i. Surveillant Microglia = smaller + multiple processes
ii. Activated Microglia = larger, rounded cell body + shorter processes
When neurones stressed-> send signals to microglia -> neurons phagocytosed
2) Astrocytes = support cells
Small, star shaped cells
➔ Provide support for development + homeostatic maintenance of nervous systems +
cerebral blood vessels
Heterogeneity across different brain regions = morphology, protein expression
Main brain blood vessels -> Blood-brain barrier = tight + not leaky
➔ Astrocytes communicate with smooth vessels to dilate/ contract -> increase/decrease
blood flow to brain to match activity
➔ Form glial scar after severe injury physically damages neurone
Neurones cannot regrow -> astrocytes fill damage cites
3) Oligodendrocytes:
Cells that form lipid rich sheath of myelin = wraps around some neurones -> increase
speed of information transmitted by other neurones
Called Schwann cells in PNS
4) Ependymal cells = ependymocytes
Columnar cells Lining ventricles in brain + central canal of spinal cord
Maintain homeostasis of CSF
Brain Matter:
Grey matter = unmyelinated cell bodies
Can conduct up to 10 m/s
White matter = areas of brain with myelin around axon bundles
Axon projections come off neurone – myelin looks white
Can conduct up to 150m/s
Fluid of CNS:
➔ Neuronal health is critically dependent on adequate blood supply
Blood vessels = Neurovascular unit: endothelial cells, astrocytes, pericytes (capillaries), smooth
muscle cells (arteries), neurones
brain cannot store oxygen e.g. heart can go 1 hour without oxygen/blood, brain can only go 2.5
minutes
