Nervous System Flashcards
Divisions of the nervous system
- CNS: integration and command center of the body
consists of brain and spinal cord - Peripheral NS: conduit between CNS and body
PNS is further subdivided into Somatic and Autonomic NS
all neural tissue outside CNS
2 cell types in NS
- neurons: consists of a body (soma) and a number of processes
- glial cells
efferent and afferent neurons
- Efferent neurons: (motor or descending) send neural impulses from CNS to peripheral tissues
- Afferent neurons: (sensory or ascending) conduct impulses from the peripheral tissues to the CNS
axons and dendrites
(length, direction)
- Axons: long and conduct impulses away from the neuronal body
- Dendrites: short and act to receive impulses from other neurons, conducting the electrical signal towards the nerve cell body
4 structural types of neurons depending on number of dendrites
multipolar, bipolar, pseudounipolar and unipolar
NEURON BODY (soma)
- contains organelles
- generates action potentials
describe glial cells and functions
- non-excitatory cells that act to support neurons
- They do not propagate action potentials
Functions: - they myelinate neurons,
- maintain homeostatic balance,
- provide structural support, protection and nutrition for neurons
four different types of glial cells
- Myelinating glia: produce the axon-insulating myelin sheath, called oligodendrocytes in the CNS and Schwann cells in the PNS (COPS)
- Astrocytes (CNS) and satellite glial cells (PNS): support and protect neurons
- microglia (CNS) : phagocytes of the CNS
- ependymal cells: line the ventricular system of the CNS
How do impulses travel through myelinated neurons?
neural impulses only travel through nodes of Ranvier (unmyelinated gaps) skipping myelin sheath; speed of neural impulse transmission increases
white and gray matter
white: myelinated axons, outermost layer of spinal cord and inner part of brain
gray: neuronal bodies and dendrites, central part of spinal cord, outermost layer of brain (cerebral cortex) and in several subcortical nuclei of the brain deep to the cerebral cortex
brain is made of four parts
cerebrum, diencephalon (hypo, epi, sub and thalamus), cerebellum and brainstem
they tell the tissues how to respond and function
spinal cord
(continues from, generates commands for, main function)
- continues from the brainstem
- generate commands for involuntary processes
- its main function is to pass information between the CNS and periphery
Peripheral nervous system
(no. of cranial, spinal nerves)
- consists of 12 pairs of cranial nerves
- 31 pairs of spinal nerve
- a number of small neuronal clusters called ganglia
- Peripheral nerves can be sensory (afferent), motor (efferent) or mixed (both)
Depending on what structures they innervate, peripheral nerves can have the following modalities;
Special - innervating special senses (e.g. eye) and is found only in afferent fibers
General - supplying everything except special senses
Somatic - innervates the skin and skeletal muscles (e.g. biceps brachii)
Visceral - supplies internal organs
cranial nerves
(type of nerves, innervates)
- are peripheral nerves that emerge from the cranial nerve nuclei of the brainstem and spinal cord
- innervate the head and neck
- numbered one to twelve according to their order of exit through the skull fissures
These nerves are motor (III, IV, VI, XI, and XII), sensory (I, II and VIII) or mixed (V, VII, IX, and X)
spinal nerves
- emerge from the segments of the spinal cord
- numbered according to their specific segment of origin
- 31 pairs of spinal nerves are divided into:
8 cervical pairs
12 thoracic pairs,
5 lumbar pairs,
5 sacral pairs, and
1 coccygeal spinal nerve
All spinal nerves are mixed, containing both sensory and motor fibers
Where do spinal nerves innervate?
the entire body, with the exception of the head
They do so by either directly synapsing with their target organs or by interlacing with each other and forming plexuses
4 major plexuses that supply the body regions;
Cervical plexus (C1-C4) - innervates the neck
Brachial plexus (C5-T1) - innervates the upper limb
Lumbar plexus (L1-L4) - innervates the lower abdominal wall, anterior hip and thigh
Sacral plexus (L4-S4) - innervates the pelvis and the lower limb
What are ganglia ?
Collection of neuronal cell bodies outside of CNS
They’re PNS equivalents to nuclei of the CNS
They can be sensory or visceral motor (autonomic)
Describe dorsal root ganglia
clusters of sensory nerve cell bodies located adjacent to the spinal cord
they are a component of the posterior root of a spinal nerve.
Describe somatic nervous system
(consists of, enables us to (functions) )
- voluntary component of PNS
- consists of: all the fibers within cranial and spinal nerves
- enable us to: perform voluntary body movements (efferent nerves) and feel sensation from the skin, muscles and joints
(afferent nerves)
Describe autonomic nervous system
- involuntary part of nervous system
- further divided into sympathetic (SANS),parasympathetic (PANS) systems, it is comprised exclusively of visceral motor fibers
- innervate all involuntary
structures of the body
Describe sympathetic nervous system
- adjusts our bodies for situations of increased physical activity
- fight-or-flight” response as it stimulates responses such as faster breathing, increased heart rate, elevated blood pressure, dilated pupils and redirection of blood flow from the skin, kidneys, stomach and intestines to the heart and muscles, where it’s needed
Describe parasympathetic nervous system
adjusts our bodies for energy conservation, activating “rest and digest” or “feed and breed activities.
