Introduction to Central Nervous System Anatomy Flashcards
Nervous system functions
- controls other systems & coordinates their activity
- evaluates stimuli from outer environment and body
- gives proper responses
The nervous system is
a highly complex part of human body
that coordinates its actions and sensory information
by
transmitting signals to and from different parts of its body
Neuron
nerve cell and all its processes
Neurons are excitable cells that are specialized for
the reception of stimuli and the conduction of the nerve impulses
The nervous system detects environmental changes that impact the body, then works in tandem with the ……. to respond to such events
endocrine system
Average size of neurons
60 – 120 cm
A neuron, or nerve cell, is an electrically excitable cell that communicates with other cells via
specialized connections called synapses
Anaxonic neurons
Have more than 2 processes and axons can’t be distinguished from dendrites
Bipolar neurons
Have 2 processes separated by cell body
Pseudounipolar neuron
Single elongated process with cell body situated to one side
Multipolar neuron
Have more than 2 processes, single axon multiple dendrities
Motor neurons that control
muscle contractions
Motor neurons shape
a cell body on one end, a long axon in the middle and dendrites on the other end
Motor neurons are divided into
Somatic
Visceral
Somatic motor neurons
- ά: extrafusal muscle fibers
- β intrafusal muscle fibers
- γ both extrafusal and intrafusal muscle fibers are innervated (supplied)
Somatic motor neurons function
Supplies skeletal muscles
Visceral motor neurons function
Supplies symphatic and para symphatic fibers
Sensory neurons shape
have dendrites on both ends, connected by a
long axon with a cell body in the middle
Types of sensory neurons
Somatic
Special
Visceral
Functions of somatic sensory neurons
Carries senses from body surface or golgi tendon organs, joint capsule, fascia
Special sensory neurons function
It carries senses such as sight, smell and taste
Visceral Sensory neurons functions
carry sensations from internal organs, glands and vascular wall
Interneurons, or associative neurons function
carry information between motor and sensory neurons
The cell body is the body of the neuron. As it contains the nucleus so?
most protein synthesis occurs here.
Nucleus of neurons diameter
3-18 micrometers
The dendrites of a neuron are
cellular extensions with many branches
The axon is
finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length
Dendrites are where the majority of input to the neuron occurs, it occurs via via
the dendritic spine
Axons function
primarily carries nerve signals away from the body and carries some types of information back to it
axon hillock
The part of the axon where it emerges from the body
most easily excited part of the neuron and the spike initiation zone for the axon
Axon hillock
The axon terminal is found at ………. and contains ……
the end of the axon farthest from the body
synapses
Schwann cells (or oligodendrocytes) are located at
regular intervals along the process (axons and, for some neurons, dendrites)
Between areas of myelin are non-myelinated areas called
nodes of Ranvier
Myelin is
fat
Myelin acts as an
insulator (substance which doesn’t allow the passage of heat or sound)
membrane coated with myelin will not conduct an impulse, why
Because fat (myelin) acts as an insulator
So, in a myelinated neuron, action potentials only occur along
the nodes of ranvier
saltatory conduction
impulses ‘jump’ over the areas of myelin - going from node to node
synapse
a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell
Synaptic boutons are
specialized structures where neurotransmitter chemicals are released to communicate with target neurons
Types of synapses
- axo-axonic
- dendro-dendritic
- axo-secretory
- somato-dendritic
- dendro-somatic, and
- somato-somatic synapses
Neurotransmitters bind to
receptors on postsynaptic neurons
When Neurotransmitters bind to receptors on postsynaptic neurons they change
transmembrane potential of postsynaptic membrane
Neurotransmitters can either be
stimulant or inhibitor
In an electrical synapse, the presynaptic and postsynaptic cell membranes are connected by special channels called
gap junctions
gap junctions function
are capable of passing an electric current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell
The main advantage of an electrical synapse is
the rapid transfer of signals from one cell to the next
Gray matter
major component of the central nervous system consisting of neuronal cell bodies
White matter
areas of the (CNS) that are mainly made up of myelinated axons, also called tracts
Tracts
myelinated axons
Nucleus
a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem
The neurons in one nucleus usually have roughly similar
connections and functions
Ganglion
a group of neuron cell bodies in the peripheral nervous system
Difference between nucleus and ganglion
Nucleus is a cluster of neurons in the central nervous system while ganglion is a group of neuron cell bodies in the peripheral nervous system
ganglia in the somatic nervous system
dorsal root ganglia and trigeminal ganglia among a few others
In the autonomic nervous system there are …… ganglia which contain ……
sympathetic and parasympathetic ganglia
the cell bodies of postganglionic sympathetic and parasympathetic neurons respectively
PNS consists of
Motor division
Sensory division
A nerve tract is
a bundle of nerve fibers (axons) connecting nuclei of the central nervous system
Fasciculus
tract
In the peripheral nervous system nerve tract is known as as a……., and has ………
as a nerve, and has associated connective tissue
OTHER CELLS of the nervous system
- Glial cells
- Mikroglialar
- Astrositler
- Ependymal cells
Receptors classified based on stimulus type
function
- Mechanoreceptors
- Thermoreceptors
- Baroreceptors
- Chemoreceptors
- Nosiseptors
- Photoreceptors
Nosiseptors
respond to potentially damaging stimuli by sending signals to the spinal cord and brain
Photoreceptors
are capable of phototransduction, a process which converts light (electromagnetic radiation) into electrical signals
Receptors are classified into 3 types based on location
Exteroceptors
Interoceptors
Proprioceptors
Exteroceptors
Located near body surface
Specialised to perceive stimuli from the external environment
Eg: receptors for vision, hearing, smell, taste
Interoreceptors
Specialised to perceive sensory information from visceral organs
Proprioceptors
Located in joint capsules, tendons, muscle fibers
, inner ear
Specialised to perceive information thar relates to an awareness of the body in space and movement
Types of proprioceptors
Muscle spindles (length of a muscle) Golgi tendons (tension of a muscle)
Types of sensory receptors depending on nerves ending
Free nerve ending
Enclosed nerve ending
Specialised receptor cell (hair cell)
Encapsulated nerve endings
Meissners corpuscles (touch) Pacinian corpuscles (pressure) Ruffini’s corpuscles (pressure) Merkels discs (touch) Proprioceptors
Muscle spindles are
stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle
Muscle spindles function
They convey length information to the central nervous system via afferent nerve fibers
Muscle Spindle consists of
Bundle of intrafusal muscle fibers
The Golgi tendon organ is
a proprioceptive sensory receptor organ that senses changes in muscle tension
(CNS) functions
• Evaluates sensations from inner & outer environment • Produces impulses for conscious & unconscious movements • Provides hormonal balance by controlling endocrine system • Coordinates intelligence, memory, learning & emotions
Parts of cns
Spinal cord
Encephalon
Parts of encephalon
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombensephalon (hindbrain)
Prosencephalon consists of
- Telencephalon
* Diencephalon
Rhombensephalon consists of
•Myelencephalon ➢ medulla oblongata •Metencephalon ➢ cerebellum, pons
spinal cord is in ……
Prosencephalon, cerebellum & brain stem-are in ….
Vertebral canal
Cranium
Somatic PNS consists of
- Cranial nerves
- Spinal nerves
Peripheral nervous system consists of
- All nn outside the CNS
- Axons of neurons in CNS
- Neurons in ganglia and their extensions
- Afferent • Efferent
Extending from the CNS are…. pairs of CRANIAL nerves and….. pairs of SPINAL nerves
12
31
CRANIAL nerves and SPINAL nerves functions
modulate somatic sensory, special sensory and motor functions
Motor devision of pns consists of
Antonomic nervous System ( symphatic/ para symphatic)
Somatic system
VISCERAL or SPLANCHNIC nn form
the peripheral part of AUTONOMIC nervous system
Autonomic nervous system parts
- Sympathetic part
- Parasympathetic part
- Enteric part
A dermatome
is the cutaneous area supplied by a single spinal nerve root
