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The Nervous System, Miranda Mancilla, Per. 2 (Cranial Nerves (VI. Abducens…
The Nervous System, Miranda Mancilla, Per. 2
Major Functions of the Nervous System
2. Integration
The nervous system process and interprets sensory input and decides what should be done at each moment.
3. Motor Output
The nervous system activates effector organs to cause a response,
1. Sensory Input
The nervous system uses its millions of sensor receptors to monitor changes occurring both inside and outside the body.
Major Divisions and Subdivisions of the Nervous System
Central Nervous System (CNS)
Structure
: Brain and Spinal cord.
Function
: Integrative and control centers.
Peripheral Nervous System
Sensory (afferent) Division
Structure
: Somatic and visceral sensory nerve fibers.
Function
: Conducts impulses from receptors to the CNS.
Motor (efferent) Division
Function
: Conducts impulses from the CNS to effectors (muscles and glands).
Structure
: Motor nerve fibers.
Autonomic Nervous System (ANS)
Structure
: Visceral (involuntary) motor nerve fibers.
Function
: Conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands.
Sympathetic Division
Function
: Mobilizes body systems during activity.
Parasympathetic Division
Function
: Conserves energy. Promotes housekeeping functions during rest.
Somatic Nervous System
Structure
: Somatic (voluntary) motor nerve fibers.
Function
: Conducts impulses from the CNS to skeletal muscles.
Function
: Communication lines between the CNS and the rest of the body.
Structure
: Cranial nerves and spinal nerves.
Major Parts of the Brain and Their Functions
Cerebellum
Is located under the cerebrum. Its function is to coordinate muscle movements, maintain posture, and balance.
Spinal Cord
Acts as a relay center connecting the cerebrum and cerebellum to the spinal cord. It performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting, and swallowing.
Cerebrum
The largest part of the brain and is composed of right and left hemispheres. It performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement.
Names of All Lobes and Their Functions
Parietal Lobe
Definition
: Either of the paired lobes of the brain at the top of the head, including areas concerned with the reception and correlation of sensory information.
Function
: Processes sensory information regarding the location of parts of the body as well as interpreting visual information and processing language and mathematics.
Temporal Lobe
Definition
: Each of the paired lobes of the brain lying beneath the temples, including areas concerned with the understanding of speech.
Function
: Involved in primary auditory perception, such as hearing, and holds the primary auditory cortex.
Frontal Lobe
Definition
: Each of the paired lobes of the brain lying immediately behind the forehead, including areas concerned with behavior, learning, personality, and voluntary movement.
Function
: Controls important cognitive skills in humans, such as emotional expression, problem solving, memory, language, judgment, and sexual behaviors.
Occipital Lobe
Definition
: The rearmost lobe in each cerebral hemisphere of the brain.
Function
: Responsible for visual perception.
Action Potential
Definition
: A brief reversal of membrane potential with a total amplitude of about 100mV. Also called a "nerve impulse".
1. Resting State
: All voltage-gated Na+ and K+ channels are closed. No ions move through volatage-gated channels.
3. Repolarization
: Na+ channels are inactivating, and voltage-gated K+ channels open. K+ flows out of the cell.
2. Depolarization
: Voltage-gated Na+ channels open. Na+ flows into the cell.
4. Hyperpolarization
: Some K+ channels remain open, and Na+ channels reset. K+ continues to leave the cell.
Spaces and Ventricles
Third Ventricle
Definition
: The central cavity of the brain, lying between the thalamus and hypothalamus of the two cerebral hemispheres.
Fourth Ventricle
Definition
: Ventricle found nearest to the back of the brain. The fourth ventricle is tent-shaped, with the peak of the tent protruding into the cerebellum and the floor of the tent being formed by the pons and medulla.
Lateral Ventricles
Definition
: Each of the first and second ventricles in the center of each cerebral hemisphere of the brain.
Layers of the Meninges
Arachnoid Mater
Definition
: A fine, delicate membrane, the middle one of the three membranes or meninges that surround the brain and spinal cord, situated between the dura mater and the pia mater.
Pia Mater
Definition
: the delicate innermost
membrane enveloping the brain and spinal cord.
Function
: Protects the central nervous system by containing the cerebrospinal fluid, which cushions the brain and spine.
Dura Mater
Definition
: The tough outermost membrane enveloping the brain and spinal cord.
Function
: Surrounds the brain and the spinal cord and is responsible for keeping in the cerebrospinal fluid
Tissues
Connective Tissue
Tissue that connects, supports, binds, or separates other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibers, and including cartilaginous, fatty, and elastic tissues.
Nervous Tissue
Integration and communication are the two major functions of nervous tissue. Nervous tissue contains two categories of cells — neurons and neuroglia.
Classification of Neurons
Bipolar Neurons
Have two processes, an axon, and a dendrite that extends from opposite sides of the cell body.
These rare neurons are found in some of the special sense organs such as in the retina of the eye and in the olfactory mucosa.
Unipolar Neurons
Have a single short process that emerges from the cell body and divides T-like into proximal and distal branches.
Found mainly in the PNS and are more accurately called pseudounipolar neurons.
Multipolar Neurons
Have three or more processes, one axon, and the rest are dendrites
Major neuron type in the CNS.
Major Parts and Functions of the Spinal Cord
Lumbar Cord
Sacral Cord
Thoracic Cord
Coccygeal Cord
Cervical Cord
Drugs that Affect the Brain
Marijuana
Inhibition is turned off and dopamine is allowed to squirt into the synapse.
Slows down movement and makes us feel calm/relaxed.
Methamphetamine
Dopamine transporters work in reverse and pump dopamine out of the cell. Excess dopamine binds to receptors and over-stimulates the cell.
Makes the user feel intense pleasure and exhileration.
Ecstasy
Seratonin transporters become 'confused' and start to do their job in reverse.
Affects seratonin pathways responsible for mood, sleep, perception, and appetite.
Alcohol
Makes GABA receptors even more inhibitory. Binds to glutamate receptors and prevents glutamate from exciting the cell.
Affects memory formation, decision making, and impulse control.
Heroine
Release of inhibitory neurotransmitters is shut down. Dopamine is then released. Dopamine inhibition is turned off.
Produces immediate feelings of sedation and well-being.
Cocaine
Blocks dopamine transporters which leaves dopamine trapped in the synaptic cleft. Dopamine binds to receptors and over-stimulates the cell.
Affects brain controlling voluntary movements. Abusers are fidgety and unable to be still.
LSD
Inhibits or excites seratonin receptors.
Feelings of wakefulness and evoking a startle response to unexpected stimulus.
Diseases Associated with the Brain
Parkinson's Disease
Definition
: Results from a degeneration of the dopamine-releasing neurons of the substantia nigra.
Persistent tremor at rest and forward-bent walking posture and shuffling gait, and stiff facial expression.
Huntington's Disease
Definition
: A fatal hereditary disorder: mutant huntingtin protein accumulates in the brain cells and the tissue dies, leading to massive degeneration of basal nuclei and later of the cerebral cortex.
Wild, jerky, almost continuous "flapping".
Alzheimer's Disease
Definition
: A progressive degenerative disease of the brain, resulting in dementia.
Exhibit memory loss, short attention span, disorientation, and language loss.
Major Nerves of the Body
Sensory Nerves
A nerve that carries sensory information toward the central nervous system (CNS).
Motor Nerves
A nerve carrying impulses from the brain or spinal cord to a muscle or gland.
Cranial Nerves
Some of these nerves bring information from the sense organs to the brain; other cranial nerves control muscles; other cranial nerves are connected to glands or internal organs such as the heart and lungs.
Divisions of the PNS of the Body
Sensory (afferent) Division
Structure
: Somatic and visceral sensory nerve fibers.
Function
: Conducts impulses from receptors to the CNS.
Motor (efferent) Division
Function
: Conducts impulses from the CNS to effectors (muscles and glands).
Structure
: Motor nerve fibers.
Autonomic Nervous System (ANS)
Structure
: Visceral (involuntary) motor nerve fibers.
Function
: Conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands.
Sympathetic Division
Function
: Mobilizes body systems during activity.
Parasympathetic Division
Function
: Conserves energy. Promotes housekeeping functions during rest.
Somatic Nervous System
Structure
: Somatic (voluntary) motor nerve fibers.
Function
: Conducts impulses from the CNS to skeletal muscles.
Cranial Nerves
VI. Abducens nerve
Controls the movement of the lateral rectus muscle in humans, responsible for outward gaze.
VII. Facial nerve
It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue.
V. Trigeminal nerve
Responsible for sensation in the face and motor functions such as biting and chewing; it is the largest of the cranial nerves.
VIII. Vestibulocochlear nerve
Transmits sound and equilibrium (balance) information from the inner ear to the brain.
IV. Trochlear nerve
Innervates only a single muscle: the superior oblique muscle of the eye, which operates through the pulley-like trochlea.
IX. Glossopharyngeal nerve
Carries afferent sensory and efferent motor information.
III. Oculomotor nerve
It enters the orbit via the superior orbital fissure and innervates extrinsic eye muscles that enable most movements of the eye and that raise the eyelid.
X. Vagus nerve
Interfaces with parasympathetic control of the heart, lungs, and digestive tract.
II. Optic nerve
Each of the second pair of cranial nerves, transmitting impulses to the brain from the retina at the back of the eye.
XI. Accessory nerve
Supplies the sternocleidomastoid and trapezius muscles.
I. Olfactory nerve
Each of the first pair of cranial nerves, transmitting impulses to the brain from the smell receptors in the mucous membrane of the nose.
XII. Hypoglossal nerve
Innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve.
Spinal Nerves
5 pairs of lumbar nerves (L1-L5)
5 pairs of sacral nerves (S1-S5)
12 pairs of thoracic nerves (T1-T12)
1 pair of tiny coccygeal nerves (Co1)
8 pairs of cervical nerves (C1-C8)
Neurotransmitters
Definition
: The "language" of the nervous system- the means by which neurons communicate.
Acetylcholine (ACh)
Function
: Excitatory or inhibitory depending on subtype of receptor. Direct or indirect.
Sites Where Secreted:
CNS
- Widespread throughout cerebral cortex, hippocampus, and brain stem
PNS
- All neuromuscular junctions with skeletal muscle; some automnomic motor endings.
Purines
ATP
Function
: Excitatory or inhabitory depending on receptor type bound.
Sites Where Secreted:
CNS
- Basal nuclei, includes Ca2+ wave propagation in astrocytes.
PNS
- Dorsal root gangliion neurons.
Adenosine
Function
: Generally inhibitory. Indirect action.
Sites Where Secreted:
Throughout the CNS and PNS.
Biogenic Amines
Norepinephrine (NE)
Function
: Excitatory or inhibitory depending on receptor type bound. Indirect action.
Sites Where Secreted:
CNS
- Brain stem, limbic system, and some area of the cerebral cortex.
PNS
- Main neurotransmitter of postganglionic neurons in the sympathetic nervous system.
Seratonin
Function
: Excitatory or inhibitory depending on the receptor type bound.
Site Where Secreted:
CNS
- Substantia nigra of midbrain, hypothalamus, the principal neurotransmitter of indirect motor pathways.
PNS
- Some sympathetic ganglia.
Dopamine
Function
: Mainly inhibitory. Indirect action and direct action.
Sites Where Secreted:
CNS
- Brain stem, hypothalamus, limbic system, cerebellum, pineal gland, and spinal cord.
Histamine
Function
: Excitatory or inhibitory depending on receptor type bound. Indirect action.
Sites Where Secreted:
CNS
- Hypothalamus.
Gases and Lipids
Carbon Monoxide (CO)
Function
: Excitatory or inhibitory. Indirect action.
Sites Where Secreted:
Brain and some neuromuscular and neuroglandular synapses.
Endocannabinoids
Function
: Inhibitory. Indirect action.
Sites Where Secreted:
Throughout the CNS.
Nitric Oxide (NO)
Sites Where Secreted:
CNS
- Brain and spinal cord.
PNS
- Adrenal gland nerves to the penis.
Function
: Excitatory or inhibitory. Indirect action.
Amino Acids
Glutamate
Function
: Generally excitatory. Direct action.
Sites Where Secreted:
CNS
- Spinal cord, widespread in brain where it represents the major excitatory neurotransmitter.
Glycine
Function
: Generally inhibitory. Direct action.
Sites Where Secreted:
CNS
- Spinal cord and brain stem, retina.
GABA
Function
: Generally inhibitory. Direct and indirect actions.
Sites Where Secreted:
CNS
- Cerebral cortex, hypothalamus, Purkinje cells of cerebellum, spinal cord, granule cells of olfactory bulb, and retina.
Peptides
Endorphins
Sites Where Secreted:
CNS
- Widely distributed in the brain and spinal cord.
Function
: Generally inhibitory. Indirect action.
Tachykinins
Function
: Excitatory. Indirect action.
Sites Where Secreted:
CNS
- Basal nuclei, midbrain, hypothalamus, and cerebral cortex.
Somastatin
Function
: Generally inhibitory. Indirect action.
Sites Where Secreted:
CNS
- Widely distributed in the brain, basal nuclei, and hippocampus,
Cholecystokinin (CCK)
Function
: Generally excitatory. Indirect action.
Sites Where Secreted:
Throughout the CNS and small intestine.
Reflex Arc
Definition
: The nerve pathway involved in a reflex action including at its simplest a sensory nerve and a motor nerve with a synapse between.
Compare and Contrast The Autonomic Nervous System
SNS stimulates skeletal muscles, whereas the ANS innervates cardiac and smooth muscle and glands.
In SNS, the motor neuron cell bodies are in the CNS, and their axons extend in spinal or cranial nerves all the way to the skeletal muscles they activate. In contrast, the ANS uses a two-neuron chain to reach its effectors.
