EXSC 224 Lecture 1: Chapter 11

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FOUR ESSENTIAL CONCEPTS IN PHYSIOLOGY
Principle of complementarity
o Physiology goes hand-in-hand with anatomy
Physiology uses gradients
o Ex. ion gradients
o Potential energy
o All types of gradients in the body
Regulate protein function by regulating its shape
o Ex. Attaching a phosphate group, changing pH, changing temp
Negative feedback regulation is essential to homeostasis
o Without homeostasis long term, we're likely to develop some disease or even
die
PATHWAYS OF THE SPINAL CORD
1. Spinocerebellar pathways
2. Dorsal column-medial lemniscal pathway
3. Spinothalamic pathways
4. Lateral corticospinal (pyramidal) pathway
THE NERVOUS SYSTEM DOES 3 THINGS
1. Sensory input
a. Detects, perceives information from tactile receptors in the skin
b. Info gathered on internal and external changes
c. Detect things in enviro and send it to the CNS
2. Integration
a. Interpretation/processing of sensory input
3. Motor output
a. Activation of effector organs (muscles and glands) produces a response
HOW IS THE NS ORGANIZED
CENTRAL NERVOUS SYSTEM
Consists of brain and spinal cord
Integrative and control centers
PERIPHERAL NERVOUS SYSTEM
Peripheral nervous system (PNS) consists of cranial nerves and spinal nerves
Nerves are only present in the PNS
Communication lines between the CNS and rest of the body
Sensory (afferent division)
o Somatic and visceral sensory nerve fibers
o Conducts impulses from receptors to the CNS
Motor (efferent) division
o Motor nerve fibers
o Conducts impulses from the CNS to effectors (muscles and glands)
o Contains the somatic NS and autonomic NS
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SOMATIC NS
Somatic motor (voluntary)
Conducts impulses from the CNS to skeletal muscles
AUTONOMIC NS
Aka ANS
Visceral motor (involuntary)
Conducts impulses from CNS to cardiac muscles, smooth muscles, and glands
Sympathetic division:
o Mobilizes body systems during activity
Parasympathetic division:
o Conserves energy
o Promotes house-keeping functions during rest
HISTOLOGY OF NERVOUS TISSUE
2 principle cell types in the NS
1. Neuroglia (glial cells)= supporting cells
a. Astrocytes (CNS)
b. Microglia (CNS)
c. Ependymal cells (CNS)
d. Oligodendrocytes (CNS)
e. Satellite cells (PNS)
f. Shwann cells (PNS)
2. Neurons= excitable cells that transmit information at synapses signals
ASTROCYTES
Most abundant, versatile, and highly branched glial cells
Cling to neurons, synaptic endings, and capillaries
Hold neurons in place, holding them in single location
Help determine capillary permeability
MICROGLIA
Small, ovoid cells with thorny processes
Migrate toward injured neurons
First line of defense; if bacteria in brain, they notify rest of body
Part of immune system
Phagocytize microorganisms and neuronal debris
EPENDYMAL CELLS
Line the central cavities of the brain and spinal column
o Ex. Ventricles
Connected to each other via tight junctions
o Water-tight barrier
Separate the CNS and interstitial fluid from cerebrospinal fluid
Produce CSF at choroid plexuses
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Range in shape from squamous to columnar
o May be ciliated
o Cilia cause movement of CSF
OLIGODENDROCYTES
Branched cells
Processes wrap around multiple axons in CNS, forming insulating myelin sheaths
Multiple sclerosis is caused by demyelination in the CNS
Produce the myelin that wraps around portions of neurons
o Speeds up rate at which neurons transmit info
SATELLITE CELLS AND SHWANN CELLS
Both found only in PNS
Not only named differently bc found in different divisions; they're also structured
differently even though they complete similar functions to cells in the CNS
Satellite cells:
o Surround neuron cell bodies in the PNS
o Similar to astrocytes
Schwann cells (neurolemmocytes)
o Surround PNS nerve fibers and form myelin sheaths
o Vital to regeneration of damaged peripheral nerve fibers
o Similar to oligodendrocytes
NEURONS (NERVE CELLS)
Primary cell in the NS
Special characteristics:
o Long-lived (100+ years)
o Amitotic, with few exceptions
o High metabolic rate
Depends on continuous supply of oxygen and glucose
High-energy cost
o Plasma membrane functions in:
Electrical signaling
Cell-to-cell interactions during development
When someone has a stroke, neurons die, but the remaining neurons can adapt to
learn to do new things and take on new tasks
The synapse is where info is transferred from one neuron to another
STRUCTURAL CLASSES OF NEURONS
Multipolar
o Many processes extend from the cell body; all are dendrites except for a
single axon
Bipolar
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