introduction to neuroanatomy
DESCRIPTION
Filename: INTRODUCTION TO NEUROANATOMY.pptTRANSCRIPT
Fernando J. Peraldo, MD, MPH
The Nervous System
the major controlling, regulatory, and communicating system in the body.
the center of all mental activity including thought, learning, and memory.
Together with the endocrine system controls the functions of the body; responsible for regulating and maintaining homeostasis.
is made up of the brain, the spinal cord, and the (peripheral) nerves that transmit information into and out of the brain and spinal cord.
The Nervous System
Central Nervous System (CNS)brainspinal cord
• Peripheral Nervous Systemnerve fibersnerve ganglia
THE HUMAN BRAIN
divided into two halves, or hemispheres, which are separated by a very deep crevice.
THE HUMAN BRAIN
The brain is made up of three major parts: the cerebrum, the brainstem, and the cerebellum.
There is a large bundle of "nerves" that relays messages between the left and right hemispheres.
brain = cerebrum + cerebellum + brainstem
View of the right side of the brain from the midline
THE HUMAN BRAIN
The brainstem a "stalk" connecting the brain and the spinal cord
- responsible for many life-sustaining functions, including regulation of breathing, heart rate, and blood pressure
- have parts concerned with regulation of sleep-wakefulness cycles and with levels of alertness
THE HUMAN BRAIN
The cerebellum
- concerned with regulating movements
- also plays an important role in procedural memory and classical conditioning
THE HUMAN BRAIN
The cerebrum
- concerned with our ability to think, to plan, to process sensory information, and to move; responsible for those abilities that make us most uniquely human
4 geographic regions, or lobes of cerebrum
Function Description Location
Motor Control of voluntary movement The back edge of the frontal lobes
Somatosensory Bodily sensations, including heat, cold, pain, pressure, and body position
The front edge of the parietal lobes
Vision Ability to see Occipital lobe
Auditory Ability to hear Top part of the temporal lobe
Speech Production (Motor Speech)
Ability to produce speech sounds "Broca's" area in the frontal lobe in the left hemisphere
Speech planning and comprehension ("sensory" speech)
Ability to plan and understand speech
"Wernicke's" area at the junction of the partiety, temporal, and occipital lobes in the left hemisphere
Biologically – based motives
Control of drives to satisfy basic biological needs, such as hunger and thirst
Hypothalamus, loacted at the bottom of the brainstem, near where the brainstem meets the cerebrum
Limbic functions Regulation of emotions "Limbic system" consisting of a group of brain areas located near the corpus callosum and extending into the temporal lobes
Summary of localization of function in the brain
localization of functions in the left hemisphere of the cerebrum
The Spinal Cord
connected to the brain, descends down the middle of the back and is surrounded and protected by the bony vertebral column
surrounded by a clear fluid called Cerebral Spinal Fluid (CSF), that acts as a cushion to protect the delicate nerve tissues against damage from banging against the inside of the vertebrae
consists of millions of nerve fibers which transmit electrical information to and from the limbs, trunk and organs of the body, back to and from the brain
1 Spinal Nerve 2 Dorsal Root Ganglion3 Dorsal Root (Sensory)4 Ventral Root (Motor) 5 Central Canal 6 Grey Matter 7 White Matter
The Spinal Cord:Ascending and Descending Spinal Tracts
Ascending tracts- within the spinal cord carry
sensory information from the body, upwards to the brain, such as touch, skin temperature, pain and joint position.
Descending tracts - within the spinal cord carry
information from the brain downwards to initiate movement and
control body functions.
Spinal Nerves
branch off the spinal cord and pass out through a hole in each of the vertebrae
carry information from the spinal cord to the rest of the body, and from the body back up to the brain.
Spinal Nerves
4 main groups of spinal nerves- Cervical Nerves "C" : (nerves in
the neck) supply movement and feeling to the arms, neck and upper trunk. Also control breathing.
- Thoracic Nerves "T" : (nerves in the upper back) supply the trunk and abdomen.
- Lumbar Nerves "L" and Sacral Nerves "S" : (nerves in the lower back) supply the legs, the bladder, bowel and sexual organs.
Spinal Cord Nerve Levels
The level of the spinal cord segments do not relate exactly to the level of the vertebral bodies i.e. damage to the bone at a particular level e.g. L5 vertebrae does not necessarily mean damage to the spinal cord at the same spinal nerve level.
Peripheral Nervous system
located outside the CNS contains nerves that extend throughout the
body Two parts to the PNS
1. Somatic nervous system - neurons deal with voluntary actions, Ex. run, play, swing, hit 2. Autonomic nervous system - generally deal with involuntary acts
The Autonomic Nervous System
a part of the nervous system that is concerned with regulating internal bodily functions that are generally considered to be involuntary or automatic, such as digestion, heart rate, blood pressure, glandular secretions, and tear production.
made up of two parts with opposite functions: 1. sympathetic nervous system
2. parasympathetic nervous system.
The Autonomic Nervous System
sympathetic nervous system- the "fight or flight" system. It prepares the body for action- active when we are anxious or otherwise emotionally aroused
- activity increases heart rate and blood pressure.
parasympathetic nervous system
- referred to as the "vegetative" system
- nurtures and rebuilds the body
- active during relaxation and rest
- Activity decreases heart rate and blood pressure and promotes digestion
ORGANIZATION OF THE NERVOUS SYSTEM
- are the basic structural and functional units of the nervous system- conducting nerve impulses- highly specialized and amitotic - generally large nerve cells
Neurons
Neurons
- generated before birth- responsible for the reception, transmission, and processing of stimuli; triggering of certain cell activities; and release of neurotransmitters
Neurons
3 parts of a neuron: - dendrites- cell body/
perikaryon- axon
Neurons
Cell Body- the metabolic center of a neuron and contains the nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles but lacks centrioles
Neurons
Dendrites - are cytoplasmic extensions, or processes, that project from the cell body- usually, but not always, short and branching, which increases their surface area to receive signals from other neurons - are called afferent processes because they transmit impulses to the neuron cell body.
Neurons
Axons- also cytoplasmic extensions, or processes,
- there is only one axon that projects from each cell body- usually elongated, carries impulses away from the cell body (efferent process)- the "transmitting" process of the neurone
Axons - may have infrequent branches called axon collaterals- Axons and axon collaterals terminate in many short branches or telodendria
distal ends of the telodendria are slightly enlarged to form synaptic bulbs
surrounded by a segmented, white, fatty substance called myelin or the myelin sheath.
SYNAPSES
morphologically specialised contacts between a bouton formed by one neuron,the presynaptic
neuron,and the cell surface of another neuron, the postsynaptic
neuron
SYNAPSES
Convert electrical signal from presynaptic cell into a chemical signal in the post synaptic cell
Transmit information by releasing chemical messengers (neurotransmitters/neuromodulators)
Formed by an axon terminal that delivers the signal and a region on the surface of another cell where a new signal is generated and a thin intercellular space called synaptic cleft
Types of Neurons
According to size and shape of their processesMultipolar – more than 2 cell processes
one axon, multiple dendrites
Bipolar – one dendrite and one axonPseudounipolar – single process close to the
perikaryon and divides into 2 branches, one extending
to the peripheral ending, the other toward the CNS
According to their functional roleMotor (efferent) neurons – control
effector organs such as muscle fibers, exocrine, and endocrine glands
Sensory (afferent) neurons – reception of
sensory stimuli from the environment and
from within the bodyInterneurons - or association neurons,
are located entirely within the CNS in which
they form the connecting link between the afferent and efferent neurons.
SUPPORT CELLS OF THE NERVOUS TISSUE
Schwann cells- Support cells in peripheral nerves- form the myelin around myelinated peripheral axons. - also envelop unmyelinated axons, but without the dense membrane wrapping which characterizes myelin.
SUPPORT CELLS OF THE NERVOUS TISSUE
• satellite cells- support cells in peripheral ganglia - cells immediately surrounding the ganglion cells as one flattened layer
SUPPORT CELLS OF THE NERVOUS TISSUE
Glial cells- most numerous cells within the central nervous system
-10 times more abundant in mammalian brain than neurons
- surround both cell bodies and their axonal and dendrite processes
- non-neuronal, supporting cells, neuroglia.
SUPPORT CELLS OF THE NERVOUS TISSUE
Glial cells Astrocytes (or astroglia)
- may be involved in the removal of transmitters from synapses and the metabolism of transmitters. - the scar-forming cells of the CNS.
- participate in the maintenance of the composition of the
extracellular fluid.
SUPPORT CELLS OF THE NERVOUS TISSUE
Glial cells Microglia
- small elongated cell with short irregular processes- phagocytic cells that representthe mononuclear phagocytic
system in nerve tissue- involved in inflammation and
repair in the adult CNS and release neutral proteases
and oxidative radicals
- mesodermal origin, derived from the cell line which also gives rise to monocytes, i.e. macrophage precursors
which circulate in the blood stream
SUPPORT CELLS OF THE NERVOUS TISSUE
Oligodendroglia - form myelin sheath around axons in the CNS - the functional homologue of peripheral Schwann
cells.- have fewer and shorter processes. - in contrast to Schwann cells in the periphery,
form parts of the myelin sheath around several
axons.- responsible for normal propagation of action potentials
SUPPORT CELLS OF THE NERVOUS TISSUE
ependymal cells - low columnar epithelial cells lining the ventricles of the brain and central canal of the spinal cord- often cilated, lack tight junctions which allows a free
exchange between cerebrospinal fluid and nervous tissue- have long basal processes and form the ventricular lining over the few CNS regions in which the blood-brain barrier is incomplete. - form tight junctions and control the exchange of
substances between these regions and surrounding nervous tissue or cerebrospinal fluid.
Review: Introduction to the Nervous System
The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory.
The various activities of the nervous system can be grouped together as three general, overlapping functions: sensory, integrative, and motor.
Neurons are the nerve cells that transmit impulses. Supporting cells are neuroglia.
Review: Introduction to the Nervous System
The three components of a neuron are a cell body or soma, one or more afferent processes called dendrites, and a single efferent process called an axon.
The central nervous system consists of the brain and spinal cord. Cranial nerves, spinal nerves, and ganglia make up the peripheral nervous system.
The afferent division of the peripheral nervous system carries impulses to the CNS; the efferent division carries impulses away from the CNS.
Review: Introduction to the Nervous System
There are three layers of meninges around the brain and spinal cord. The outer layer is dura mater, the middle layer is arachnoid, and the innermost layer is pia mater.
The spinal cord functions as a conduction pathway and as a reflex center. Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts.
End of lecture
Thank you