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Physio Notes
LECUTRE 1
Physiology: function of the human body, cells, organs and bodily systems.
Levels of organisation of physiology:
1. Organism composed of organ systems
2. Organ systems composed of organs
3. Organs composed of tissues
4. Tissues composed of cells
5. Cells contain organelles
6. Organelles composed of interacting molecules
7. Molecules composed of atoms
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Homeostasis: is the ability to maintain stability of the internal conditions despite
changing external factors (STAYING THE SAME). All organs and systems play a vital role in
keeping stability of the internal environment. In dynamic equilibrium state the body’s
functional activities should run smooth, given that cellular needs are adequate. E.g.
thermostat… RECEPTORS ------- CONTROL CENTER ------- EFFECTOR -------HOMEOSTASIS
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Positive Feedback Loop: enhance or amplify changes; this tends to move a system away
from its equilibrium state and make it more unstable. A process that accelerates to
completion stage. E.g. child birth, blood clotting
Negative Feedback Loop: tend to dampen or buffer changes; this tends to hold a system
to some equilibrium state making it more stable. There are more negative feedback to
maintain. E.g. Thermoregulation (sweating)
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THE NERVOUS SYSTEM: is the master control and also the communication centre. E.g.
action, emotion and thought. The nervous system has three overlapping functions:
Sensory Input, Integration and Motor Output.
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Subdivisions of Nervous System:
• Central Nervous System (Spinal Cord and The Brain) – is responsible for
integrating, coordinating and processing sensory data, as well as motor
commands.
• Peripheral Nervous System (Spinal Nerves, Cranial Nerves, Ganglia) – includes
all the neural tissue outside the CNS. There are two subdivisions: Sensory
(AFFERENT) Division and Motor (EFFERENT) Division.
The Sensory/ Afferent Division: from receptors to CNS
• Visceral Afferent Fibres/ Receptors – monitors internal organs
• Somatic Afferent Fibres/ Receptors – provides position, touch, pressure, pain and
temperature sensations from skin, skeletal muscles and joints.
Motor/ Efferent Division: from CNS to effector Organs
• Somatic Motor Division/ System: somatic motor nerve fibres conduct impulse from
CNS to skeletal muscles, voluntary somatic reflexes. This division also controls
skeletal muscle contractions.
• Autonomic/ Involuntary Nervous System: visceral motor nerve fibres regulate
activity of smooth muscles, cardiac muscle and glands.
• Sympathetic Division: “Fight or Flight” system, action
• Parasympathetic Division: “resting and digesting” system, digestion
Functional Types of Neurons:
• Sensory (afferent) neurons – identifies changes in the body and external
environment. The information is either sent to the brain or spinal cord.
• Interneurons (association neurons) – lies between sensory and motor pathways in
CNS and the human body consists of 90% of interneurons. Interneurons process,
store and retrieve information.
• Motor (efferent) neurons – sends the signal from the CNS out to the effectors
(muscles and gland cells) which creates a response.
THE BRAIN AND CRANIAL NERVES
There are four major regions of the brain: Cerebrum, Cerebellum, Diencephalon, and
Brain Stem
CEREBRUM – consists of five areas called:
• The frontal: responsible for voluntary motor function, motivation, planning and
memory, mood, emotion and social judgement.
• The parietal: This receives and integrates sensory information (taste and some
visual processing). The somatic sensory association area is a part of this lobe,
which locates touch or pain, shape, weight and texture of an object and position
of limbs.
• The occipital: This is visual centre of the brain. The visual association area
identifies the objects we see.
• The temporal: which are the areas for hearing, smell, learning, memory and
emotional behaviour. Recalls the auditory of a person or music.
• The insula: process, spoken language, taste and integrates sensory info from
visceral receptors
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Integrative centres:
• Broca area: speech centre, regulates breathing and vocalization for speech
• Prefrontal cortex: coordinates information from association areas and predicts
consequences
• Frontal eye field: controls learned eye movements
• Wernicke area (general interpretive area): analytical centre receives info from all
sensory association areas.
Hemispheric lateralization:
• Left cerebral hemisphere – categorical hemisphere: specialised for spoken and
written language, sequential and analytical reasoning and analyses data in
linear way
• Right cerebral hemisphere – representational hemisphere: perceives info more
holistically, perception of spatial relationships, pattern, comparison of special
senses, emotional context, imagination and insight, music and artistic skill.
Limbic system: motivational system, plays a role in emotion and memory (amygdaloid
body) and includes nuclei and tracts along the border of the cerebrum and
diencephalon.
CEREBELLUM: processes input from other areas of the brain, spinal cord and sensory
receptors to provide precise timing for coordinated, smooth movements of the skeletal
muscular system. The cerebellum maintains balance and equilibrium by adjusting
postural muscles in the body.
DIENCEPHALON: consists of the Epithalamus (pineal gland: secretes the hormone
melatonin, regulates day-night cycles and reproductive function), Thalamus (is the
pathway to the cerebral cortex, and it also filters incoming sensory info and passes small
portions of it to the cerebral hemispheres) and the Hypothalamus (main control and
integration centre of the ANS and endocrine system, and is stimulated by sensory info
from cerebrum, brain stem and spinal cord. As well as changes in composition of the CSF
and interstitial fluid and chemical stimuli in the circulating blood (lacks BBB) ).
BRAIN STEM: The brain stem consists of the medulla oblongata, pons and the midbrain
area.
MIDBRAIN: also called mesencephalon, region of the
developing vertebrate brain containing cranial nerves that stimulate
the muscles controlling eye movement, lens shape, and pupil diameter. These masses of
nerves form the nuclear complex of the oculomotor nerve and the trochlear nucleus.
The substania nigra, the motor centre sends inhibitory signals to the thalamus. It is also
the reflex centre of the brain e.g.. jumping when startled. Reticular formation: somatic
motor control (maintain tone, balance and posture), cardiovascular control, pain
modulation, sleep consciousness and alertness (reticular activating system) and
habituation (learning to ignore repetitive, inconsequential stimuli).
PONS: portion of the brain lying above the medulla oblongata and below
the cerebellum and the cavity of the fourth ventricle. This is the point of origin or
termination for four of the cranial nerves that transfer sensory information and motor
impulses to and from the facial region and the brain. The pons also serves as a pathway
for nerve fibres connecting the cerebral cortex with the cerebellum.
MEDULLA OBLONGOTA: also called medulla, the lowest part of the brain and the lowest
portion of the brainstem. The medulla oblongata is connected by the pons to
the midbrain and is continuous posteriorly with the spinal cord. Like the cerebrum and
the cerebellum consists of both myelinated (white matter) and unmyelinated (gray
matter) nerve fibres. A complex network of medullary nerve cells in the central nervous
system enables the medulla to carry on complex integrative functions. The medulla also
contains several functional centres that control autonomic nervous activity, regulating
respiration, heart rate, and digestive processes. Other activities of the medulla include
control of movement, relaying of somatic sensory information from internal organs, and
control of arousal and sleep.
CRANIAL NERVES: in vertebrates, any of the paired nerves of the peripheral nervous
system that connect the muscles and sense organs of the head and thoracic region
directly to the brain. There are 12 pairs of cranial nerves, olfactory (I), optic (II),
oculomotor (III), trochlear (IV), trigeminal (V), abducent (VI), facial (VII),
vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal
(XII). Lower vertebrates (fishes, amphibians) have 10 pairs.
SPINAL CORD: major nerve tract of vertebrates, extending from the base of
the brain through the canal of the spinal column. It is composed of nerve fibres that
mediate reflex actions and that transmit impulses to and from the brain (consists also
the peripheral nerves) (CONDUCTION). LOCOMOTION – repetitive, coordinated actions of
several muscle groups. Central pattern generators are pools of neurons providing control
of flexors and extensors (walking). REFLEXES – involuntary, stereotyped responses to
stimuli (remove hand from hot stove).
GRAY MATTER: sensory nuclei receive and relay info from peripheral receptors. Motor
nuclei issue motor commands to peripheral effectors.
WHITE MATTER: white column, bundles of myelinated axons that carry signals up and
down to and from brainstem. There are three pairs, posterior, lateral and anterior
columns. Each column is filled with named tracts, meaning that the fibres with similar
origin, destination and function).
SPINAL NERVES: 31 pairs arise to form the spinal cord and supply all parts of the body,
except for the head. There are 8 pairs of cervical spinal nerves, 12 pairs of thoracic
nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerve.
The branches of the spinal nerves:
• Dorsal Ramus – innervates muscles, points and skin of the back
• Ventral Ramus – innervates structures in the lateral and anterior trunk
• Communicating Rami – contain axons of sympathetic neurons in the thoracic and
upper lumbar segments, sympathetic division of ANS (Fight or Flight)
Cutaneous Innervation and Dermatomes – each spinal nerve receives sensory input from
a specific area of the skin called dermatome. A total loss of sensation requires
anaesthesia of 3 successive spinal nerves.
Reflexes – rapid, automatic responses to specific stimuli, preserves homeostasis,
response shows little variability. Somatic reflexes – stimulate skeletal muscles, patellar
reflex. Visceral reflexes – regulate activity of smooth muscles, heart and glands,
secretion of saliva, pupillary reflex.