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Emely Casillas P1 Nervous System - Coggle Diagram
Emely Casillas P1 Nervous System
Major functions of the nervous system
Sensory function
Provided by sensory receptors, which detect internal or external
changes.
Information travels from receptors to sensory neurons, which
transport information into the CNS
Integrative function
Coordination of sensory information in the CNS.
Processing of this information is the basis for decision-making
Motor function
Nerve impulses (CNS) are conducted along motor neurons to effectors
Effectors are muscles or glands that respond to decisions made in the CNS
Major divisions and subdivisions of the nervous system (include all subdivisions of CNS
and PNS)
Peripheral nervous system (PNS)
Consists of nerves that connect the CNS to body parts
Consists of cranial nerves, arising from the brain, and spinal
nerves, arising from the spinal cord
Contains sensory and motor divisions
The motor part of the PNS is made up of 2 portions:
Somatic nervous system, which connects the CNS to skeletal muscles and the skin, and oversees conscious activities
Autonomic nervous system, which connects the CNS to viscera, and controls subconscious activities
Autonomic nervous system (ANS)
Portion of the PNS that functions constantly and independently,
without conscious effort
Controls visceral motor functions of smooth muscle, cardiac
muscle, and glands
Helps maintain homeostasis, responds to emotional stress, and
prepares the body for strenuous activity
Controls heart rate, blood pressure, breathing rate, body
temperature
Two divisions
Sympathetic division: active in conditions of stress or
emergency (fight or flight).
Parasympathetic division: active under normal, restful
conditions (rest and digest)
neurons
A preganglionic neuron, that leaves the CNS, and synapses with
one or more neurons, which have cell bodies in an autonomic
ganglion in the PNS.
A postganglionic neuron, whose fiber (axon) leaves an
autonomic ganglion, and innervates a visceral effector.
Central nervous system (CNS)
Made up of the brain and spinal cord.
Responsible for integration of information and decision-making.
Types of nerves
Sensory (afferent) nerves conduct impulses to the CNS; their axons are called sensory fibers
Motor (efferent) nerves carry impulses from the CNS to effectors;
their axons are called motor fibers
Mixed nerves carry both sensory and motor fibers; most nerves are of this type.
General Functions of the Nervous System
Sensory function: Provided by sensory receptors, which detect internal or external changes, Information travels from receptors to sensory neurons, which transport information into the CNS
Integrative function: Coordination of sensory information in the CNS, Processing of this information is the basis for decision-making.
Motor function: Nerve impulses (CNS) are conducted along motor neurons to effectors, Effectors are muscles or glands that respond to decisions made in the CNS
Tissues (structure & function of neurons and neuroglia)
Structural Classification of Neurons
Multipolar neurons: have many dendrites and one axon arising from their cell bodies;most neurons with cell bodies in CNS (interneurons and motor neurons) are multipolar.
Bipolar neurons have 2 processes extending from the cell body, a dendrite and an axon; foundin some of the special senses, such as the eyes, nose, and ears.
Unipolar neurons have only 1 process extending from the cell body; outside the cell body, it soon splits into 2 parts that functionas 1 axon; the peripheral process has dendrites near a peripheral body part, and the central processruns into the CNS; the cell bodies are found in ganglia outside the CNS; these are sensory neurons
Functional Classification of Neurons
Sensory (afferent) neurons: conduct impulses from peripheral
receptors to the CNS; usually unipolar, although some are bipolar.
Interneurons (association or internuncial neurons): multipolar
neurons lying within the CNS that form links between other
neurons; the cell bodies of some interneurons aggregate in specialized masses called nuclei.
Motor (efferent) neurons: multipolar neurons that conduct
impulses from the CNS to peripheral effectors (muscles or glands).
Neuroglia (glial cells, “nerve glue”) are cells that support neurons
Central nervous system neuroglia
Microglia: small cells that function as phagocytes for bacterial cells and cellular debris, and produce scar tissue in sites of injury.
Oligodendrocytes: form the myelin sheath around axons in the brain and spinal cord
Ependymal cells: produce cerebrospinal fluid in CNS
Astrocytes: lie between blood vessels and neurons:
Formation of the blood-brain barrier, which protects brain tissue from chemical fluctuation and prevents entry of many substances
(Structural support)
Peripheral nervous system neuroglia
Schwann cells: the myelin-producing neuroglia of the PNS.
Satellite cells: provide protective coating around cell bodies of
neurons in the PNS.
Classification of neurons
Major aspects of nervous system: sensory input, integration and processing (decision-making), and motor output (response).
Main cell types in the nervous system
Neuroglia: cells that support, nourish, protect, and insulate
neurons.
Neurons: cells that communicate, via electrical impulses, with
other neurons or other tissues
A neuron contains a cell body, tubular cytoplasm-filled dendrites, and a tubular, cytoplasm-filled axon
Myelin Sheath: Larger axons are enclosed by myelin sheaths; they are called myelinated fibers,Narrow gaps in the myelin sheath are called nodes of Ranvier , Myelin sheath increases conduction speed of nerve impulses.
Connective Tissue Coverings
The brain and spinal cord are surrounded by 3 membranes called meninges that lie between the skull bones & vertebrae and the soft CNS tissues.
Dura mater
Outermost layer of meninges
Made up of tough, dense connective tissue, and is very thick.
The sheath around the spinal cord is separated from the vertebrae by an epidural space.
Arachnoid mater
The middle layer of meninges.
Between the arachnoid and pia mater is the subarachnoid
space, which contains cerebrospinal fluid (CSF)
Pia mater
The innermost layer of the meninges.
Epineurium: outer covering of a nerve
Perineurium: covering around fascicles (bundles) of nerve fibers
Endoneurium: covering around individual nerve fibers (axons).
Major parts and functions of the brain
Cerebrum: largest portion; associated with higher mental functions, and sensory & motor functions
Cerebrum is largest portion of the mature brain
Corpus callosum: flat bundle of nerve fibers that connects the
hemispheres.
features
Gyri (singular is gyrus): ridges.
• Sulci (singular is sulcus): grooves.
• Fissures (longitudinal and transverse): deep grooves
Four lobes of the cerebrum are named according to the bones
they underlie: frontal, parietal, temporal, and occipital lobes
functions
Personality
Intelligence.
Integrates information for reasoning.
Stores information for memory.
Initiating voluntary muscular movements.
Interpretation of sensory input.
Diencephalon: processes sensory input and controls many homeostatic processes
Cerebellum: coordinates muscular activity.
located beneath the occipital lobes of the cerebrum,
posterior to the brainstem.
A thin layer of gray matter called the cerebellar cortex lies outside a core of white matter called the arbor vitae
Functions
Integrates sensory information about the position of body parts
Maintains posture.
Ensures that movement occurs in the desired manner.
Coordinates skeletal activity.
Brainstem: coordinates and regulates visceral activities, and connects different parts of the nervous system.
Midbrain: Contains main motor pathways between cerebrum and lower portions of the nervous system (Located between the diencephalon and pons)
Pons: Contains centers that help regulate the rate and depth of breathing (Lies between the midbrain and medulla oblongata)
medulla oblongata: transmits all ascending and descending impulses between the brain and spinal cord.
Cardiac center: alters heart rate.
Vasomotor center: controls vasoconstriction & vasodilation of blood vessels; helps control blood pressure.
Respiratory center: Controls rate and depth of breathing
sensory areas
Cutaneous senses: anterior parietal lobe
Visual area: posterior occipital lobe
Auditory area: posterior temporal lobe
Taste area: base of central sulcus and insula
Smell area: deep in temporal lobe.
Broca’s motor speech area is in the frontal lobe, usually on the left side; controls muscle movements for speech
Ventricles: a series of connected cavities within the cerebral
hemispheres and brainstem
Choroid Plexuses:Secrete cerebrospinal fluid (CSF) into the ventricles; most CSF arises in the lateral ventricles
diencephalon: lies between the cerebral hemispheres and above the midbrain.
thalamus
Sorting and directing sensory information arriving from other
parts of the nervous system to the cerebral cortex (relay center
Channels all sensory impulses, except those for the sense of smell.
Produces general awareness of the sensation, such as pain,
touch and temperature
Hypothalamus
The hypothalamus maintains homeostasis by regulating a wide
variety of visceral activities and by linking the endocrine system with the nervous system:
The Limbic System: in the area of the diencephalon, controls emotional experience and expression
Major parts and functions of the spinal cord
Numbered in sequence: 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves
Spinal cord: Begins at the base of the brain
Cervical enlargement: A thickened area near top of spinal cord, Provides nerves to upper limbs.
Lumbar enlargement:A thickened region near the bottom of the spinal cord, Gives rise to nerves that serve the lower limbs.
Cauda equina (horse’s tail): Structure formed where spinal cord tapers to a point inferiorly, Consists of spinal nerves in the lumbar & sacral areas
Spinal cord consists of 31 segments, each of which connects to a pair of spinal nerves
Functions
Major functions: transmit impulses to and from the brain, and to house spinal reflexes
Ascending tracts carry sensory information to the brain; descending tracts carry motor information from brain to muscles or glands
Spinal reflexes: controlled by reflex arcs that pass through the spinal cord.
Action potential & the Nerve Impulse
Membrane Potential: the charge inside a cell.
Resting Membrane Potential: the charge in a cell when it is at rest; this is about -70 mV in neurons
Threshold stimulus: a stimulus strong enough to cause so many Na+ions to enter neuron that potential changes from -70 to -55 mV (the threshold potential).
Refractory period: period during and after an action potential, during which a threshold stimulus will not cause another action potential
Limits frequency of action potentials
Ensures the impulse is only transmitted in one direction –down the axon.
Types of Impulse Conduction
Saltatory conduction: Occurs in myelinated axons,
The myelin sheath insulates axons from ion movement across the cell membrane
Continuous conduction: Occurs in unmyelinated axons,
Conduct impulses sequentially over the entire length of their
membrane
Cranial nerves
Twelve pairs of cranial nerves arise from the underside of the brain
Most are mixed nerves, containing sensory & motor nerve fibers, but some are only sensory, and others are primarily motor
The first pair arises from the cerebrum, and the second pair from the thalamus, but most arise from the brainstem
The 12 pairs are designated by number and name; the numbers are in order, from superior to inferior.
Spinal nerves
31 pairs of spinal nerves arise from spinal cord
Cervical Plexuses (C1-C4): lie on either side of the neck; supply muscles and skin of the neck; include the phrenic nerves, which control the diaphragm
Brachial Plexuses (C5 –T1): arise from lower cervical and upper thoracic nerves; supply muscles and skin of arms, forearms, and hands; lead into the upper limbs; include the musculocutaneous, ulnar, median, radial, and axillary nerves
Lumbosacral Plexuses (L1-S4): arise from the lower spinal cord; supply muscles and skin of the lower abdomen, external genitalia, buttocks, and
Anterior branches of the thoracic spinal nerves do not form plexuses, but become the intercostal nerves
Neurotransmitters
A synapse is a junction between 2 communicating neurons
The small gap between the neurons is called the synaptic cleft; the impulse must be conveyed across the cleft
The neuron sending the impulse is the presynaptic neuron.
The neuron receiving the impulse is the postsynaptic neuron.
Communication is accomplished by a chemical called a
neurotransmitter, which is stored and released from synaptic vesicle
Neurotransmitters
There are more than 100 neurotransmitters
Neurotransmitters include acetylcholine, amino acids,
neuropeptides
Action of neurotransmitter depends on type of receptors in a
specific synapse.
Some neurons produce one type of neurotransmitter, while others produce two or three
Neurotransmitters are the chemical messengers in a synapse, that convey an electrical impulse from a neuron to another cell.
Compare & contrast the autonomic nervous system
Neurotransmitters are the chemical messengers in a synapse, that convey an electrical impulse from a neuron to another cell.
Autonomic nervous system: controls involuntary effectors (smooth and cardiac muscles and glands).
The somatic nervous system has sensory and motor pathways, whereas the autonomic nervous system only has motor pathways
Reflex arc (major parts & functions)
The routes nerve impulses travel are called neural pathways, the simplest of which is a reflex arc
Reflex arcs provide the basis for involuntary actions called reflexes
Components of a reflex arc
A sensory receptor that detects changes.
A sensory neuron, that carries the information from a receptor
toward the CNS.
An interneuron in the CNS (reflex center).
A motor neuron, that carries a command to effectors.
An effector (muscle or gland that carries out the reflex) that responds to the initial change
Reflexes: automatic responses to changes (stimuli) inside or outside of the body, that help maintain homeostasis
Withdrawal reflex: Occurs in response to touching something painful, such as stepping on a tack (or laying a hand on a hot stove).
patellar (knee-jerk) reflex is an example of a simple reflex; it has
only 2 neurons, sensory & motor, and lacks an interneuron
Disorders/Diseases
Cerebrovascular accidents
Symptoms include dizziness, numbness, weakness on one side of the body, and problems with talking, writing, or understanding language
a loss of blood flow to part of the brain, which damages brain tissue
caused by blood clots and broken blood vessels in the brain.
autism
Autism spectrum disorder (ASD) is a developmental disability caused by differences in the brain.
signs
not responding to their name.
avoiding eye contact.
not smiling when you smile at them.
getting very upset if they do not like a certain taste, smell or sound.
repetitive movements, such as flapping their hands, flicking their fingers or rocking their body.
Alzheimer's disease
most common type of dementia. It is a progressive disease beginning with mild memory loss and possibly leading to loss of the ability to carry on a conversation and respond to the environment.
Alzheimer's disease involves parts of the brain that control thought, memory, and language
Spinal cord injury
An injury higher on the spinal cord can cause paralysis in most of the body and affect all limbs (called tetraplegia or quadriplegia). A lower injury to the spinal cord may cause paralysis affecting the legs and lower body (called paraplegia)
Meningitis
inflammation (swelling) of the protective membranes covering the brain and spinal cord.
bacterial or viral infection of the fluid surrounding the brain and spinal cord usually causes the swelling. However, injuries, cancer, certain drugs, and other types of infections also can cause meningitis
Multiple sclerosis
Multiple sclerosis (MS) is a potentially disabling disease of the brain and spinal cord (central nervous system)
In MS, the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body. Eventually, the disease can cause permanent damage or deterioration of the nerves
Drugs of abuse (Mouse Party)
Heroin
pain signals, stress response, emotional attachment
opiates are natural pain killers, ,morphine, a drug related to heroin is used as a pain killer
Ecstasy
mood, sleep, perception and appetite
"reward" pathway
addictive properties
Marijuana
removes unnecessary short memories
slows down movement, feel relaxed and calm
methamphetamine
"reward" pathway
feels pleasure and exhilaration
alcohol
affects areas of brain involved in memory formation, decision making, and impulse control
cocaine
"reward" pathway
active in part of brain controlling voluntary movements
fidgety, unable to sit still
LSD
excite locus coeruleus
feelings of wakefulness and evoking a startle response to unexpected stimulants