Physiology 2130 Lecture Notes - Lecture 6: Golgi Tendon Organ, Cranial Nerves, Preganglionic Nerve Fibers
29 May 2018
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Module 6 – Outcomes
Draw and label a diagram of the human brain, showing all the major regions, important gyri and sulci, and the major
functional areas of movements, sensory, vision, hearing, speech, and so on.
Basic Structure of the Brain:
• There are two cerebral hemispheres
o The left hemisphere sends signals to activate muscles on the right side of the
body, and vice versa
• The brain stem
o Controls some of the most basic functions of the body
▪ Like: HR, respiration, etc.
o The brain stem is made up of the midbrain, pons and medulla oblongata
▪ The medulla is continuous with the spinal cord
• At the back or posterior region and just above the brain stem is the cerebellum
o Responsible for coordinated movement
• The diencephalon is made up of the thalamus and hypothalamus
• There are many bumps (gyri) and dips (sulci) on the surface of the brain
o These folds are most prominent in humans and increase the SA of the brain
o The locations of the gyri and sulci are quite consistent across individuals and
are so prominent they have different names
• Each cerebral hemisphere can be divided into four lobes
o Parietal, occipital, frontal and temporal
Functional Structure of the Brain:
• Each region of the brain has a specific function, and some are organized in an extremely specific manner
• Note: four different views of the brain, different structure from each view
• Lateral view
o Frontal lobe:
▪ Primary cortex: processes input from skeletal muscles throughout the body
▪ Premotor cortex (motor association area) and the prefrontal cortex: integrate
movement information with other sensory inputs to generate perception of stimuli
o Parietal lobe:
▪ Primary somatosensory cortex: receives input from the major sense organs
▪ Association areas: integrate sensory information with other association area of the
cortex to for meaningful perceptions
o Cerebellum:
▪ Processes sensory information and coordinated the execution of movement in the
body
▪ As the structure with the largest number of neurons in the brain, the cerebellum
receives input from somatic receptors, receptors fore equilibrium and balance and
motor neurons from the cortex
o Temporal lobe:
▪ Primary auditory cortex and auditory association areas: receive and process signals
from auditory nerves and integrate them with other sensory inputs
▪ Other areas: involved in olfaction and mediating short-term memory storage and
recall
o Occipital lobe:
▪ Responsible for vision
▪ Primary visual cortex: receives input directly from the optic nerve
▪ Visual association areas: further process visual information and integrate it with
other sensory inputs
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• Medial view
o Corpus collosum:
▪ Dense bundle of nerve fibers that serves as a pathway and connection between the two cerebral
hemispheres
▪ This connection allows the brain to integrate sensory and motor information from
both sides of the body and coordinate whole-body movement and function
o Pituitary gland:
▪ Primarily regulates endocrine organs
▪ The anterior pituitary is derived from epithelial tissue of the pharynx
▪ The posterior pituitary derives from neural tissue of the hypothalamus
▪ Anterior pituitary hormones – LH, FSH, ACTH, TSH, GH and prolactin
▪ Posterior pituitary hormones – vasopressin and oxytocin
▪ Pituitary function is regulated by the hypothalamus
o Pons:
▪ Acts as a relay station for transferring information between the cerebellum and the
cerebral cortex
▪ Also coordinates and controls breathing
o Diencephalon:
▪ Thalamus: receives sensory inputs from the spinal cord and integrates sensory
information before sending it to the cortex
▪ Hypothalamus: controls a variety of endocrine functions, mainly through directing
the release of hormones
o Midbrain:
▪ Or mesencephalon
▪ Bridges the lowers brainstem with the diencephalon
▪ Primary function is controlling eye movements and exerts some control over
auditory and visual motor reflexes
o Medulla
▪ Portion of the brainstem that has primary control over involuntary functions such as
breathing, blood pressure and swallowing
▪ Fibres from the corticospinal tract, which originate in the motor cortex, cross over
to the opposite side of the spinal cord to innervate muscles on the opposite side of
the body
• Ventral view
o Optic chiasma:
▪ Optic nerves from each eye meet here, where they cross over and continue on to
the lateral geniculate bodies on the thalamus
▪ From there the axons extend to their respective hemisphere on the primary visual area of the
occipital lobe
o Brain stem:
▪ Extension of the spinal cord and consists of three regions
▪ From left to right on figure
• Midbrain, pons and medulla
▪ The brainstem is the center for many involuntary functions
▪ Incorporates 9 cranial nerves
• Dorsal view
o Primary motor cortex
▪ Posterior end of the frontal lobe
▪ Processes information relating to skeletal muscle movement
▪ When electrically stimulated, this region will cause a specific muscle to contract
▪ Arrangement is very specific
o Primary somatosensory cortex
▪ Anterior end of the parietal lobe
▪ Receives sensory information from the opposite side of the body
▪ Processes sensations of pain, temperature, touch and vibration
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o Language and mathematical area
▪ Most often located in the left hemisphere
▪ Serves as a general interpretative center for visual and auditory information
▪ Generates written and spoken responses
Name two main types of brain cells.
• The brain is made up of tens of billions of neurons and glial cells
• Neurons are the information transmitting and processing cells of the body
o Yet they constitute only a small percentage of the brain
• Glial cells: provide the necessary environment for neurons to function properly
o 90% of the brain
Neurons:
• Three basic types of neurons found in mammals based on the number of processes that emerge from the cell body
• Bipolar neurons
o Have two processes extending from the cell body
o Specialized neuron found in the retina of the eye
• Unipolar neurons
o Have one process extending from the cell body
o Located in the peripheral nerves outside the CNS and generally sensory in
nature
o Transmit signals to and from the spinal cord
o The cell body lies in the middle and off to one side of the axon
• Multipolar neurons
o Contain many branching dendrite and one axon
o Most common in the CNS
Glial Cells:
• Glial ells ae the suppot ells of the ai, as the aitai the deliate iteal eioet of the CN“
• There are roughly 5x the number of glial cells than neurons
• Have structural role (gluing things together) but also a regulatory role (nutrients and specific enviro)
• They perform these functions by regulating the passage of substances between the blood and the brains interstitial
space
• There are several types of glial cells including: astrocytes, microglia, and oligodendrocytes (produce myelin)
Draw and label a chemical synapse.
• The ao teial of the pesapti ell … hih otais
o Voltage-gated calcium-ion (Ca+) channels
o Synaptic vesicles containing the nt
o Mitochondria
• The synaptic cleft
• The postsapti ell … hih otais
o Chemical receptors
o Chemically gated or ligand gated ion channels
▪ Opens when a chemical attaches
Describe the events underlying synaptic transmission.
1. Presynaptic neurons synthesize nt that are stored in the synaptic vesicles
2. An AP in the presynaptic neuron depolarizes the membrane and activates voltage gated Ca+ channels – Ca+ flows into
the axon terminal
3. Ca+ causes the synaptic vesicles to fuse to the wall of the synaptic terminal, causing exocytosis and the release of the
nt
4. The nt diffuses across the synaptic cleft and acts on chemical receptors found on the postsynaptic cell membrane
5. Receptors cause the opening of the chemically gated ion channels
6. The postsynaptic membrane potential changes, causing a depolarization or hyperpolarization depending on the type
of nt. A depolarization increases probability of an AP and hyperpolarization decreases the likelihood.
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