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Nervous System P.1 …
Nervous System P.1 Frida Hernandez
Major Divisions and Subdivisions of the Nervous System
Neurons
- Cells that communicate (with electric impulses) with other neurons & tissues
Central nervous system (CNS)
:- 2 groups; Made up of the Brain and Spinal Cord; decision-making
Peripheral Nervous System (PNS)
- Cranial and Spinal cord that connects the CNSto the rest of the body
Sensory (
Afferent
) and Motor (
Efferent
) Divisions.
Somatic Nervous System
- Controls voluntary skeletal muscles
Autonomic Nervous System
- Controls involuntary effectors (smooth and
cardiac muscles and glands).
Drugs of abuse (Mouse Party)
Heroine
- affects Central N.S; It creates a feeling of sedation (addictive)
Marijuana
- affects memory, attention, and the dopamine receptors
LSD
- affects the serotonin of the brain; the locus coeruleus is affected
Methopholine
- affects the dopamine of the brain and is highly addivtive
Ecstasy
- affects the serotonin of the brain; mood, sleep, and appetite affected
Alcohol
- affects the GABA and Glutamate part of the brain; The memory, and impulse control
Cocaine
- affects the dopamine of the brain and the voluntary part of the brain
Major functions of the nervous system
Sensory Input [
Eyes
] , Integration and
Processing (decision-making) [
Brain / Spinal Cord
], and Motor Output (response) [
Effectors; Muscles
]
Thinking, Movement, Internal
Processes of Physiology.
Cranial nerves
Twelve pairs
of cranial nerves; most are
mixed nerves
first pair arises from the cerebrum, and the second pair from the thalamus, but most arise from the brainstem.
12 pairs
are designated by number and name; the numbers are in order, from superior to inferior
Major Parts and Functions of the Brain
4 Main Parts of the Brain
Cerebrum:
Largest portion; associated with higher mental functions, and sensory & motor functions.
Diencephalon
: Processes sensory input and controls many homeostatic processes.
Cerebellum
: Coordinates muscular activity.
Brainstem
: coordinates and regulates visceral activities, and connects different parts of the nervous system.
Meninges
- the three membranes that lie between the skull bones
Dura mater
- Outermost Layer of the meninges
Arachnoid mater
- Middle layer of meninges
Pia mater
- Innermost layer of meninges
Classification of Neurons
Neuroglia
- Cells that support, nourish, protect and insulate neurons
Neurotransmitters
- Chemical messenger in the synapse that conveys an electrical impulse from a neuron to another cell.
Cell Body (Soma)
- Major organelles w/ Nucleu
Axon
- 1 in each neuron
Dendrites
- Impulse towards the cell body
Neuroglia
- Cells that support neurons
Myelin Sheath
- Increase conduction of nerve impulse
Major parts and Functions of the Spinal Cord
Spinal Cord
- Base of the brain
Cervical enlargement
- Thickened area near top of spinal cord.
Lumbar enlargement
- Thickened region near the bottom of the spinal cord.
Cauda equina (horse’s tail)
- End of spinal cord
Major functions
- transmit impulses to and from the brain, and to house spinal reflexes.
Action Potential & the Nerve Impulse
Excitatory stimulus opens chemically-gated
Na+ channels
Threshold stimulus
- stimulus strong enough to cause so many Na+ ions to enter neuron
Voltage-gated Na+ channels
open,
changing charge to about +30 mV; this is called an
Action Potential
Reaching an action potential is
All-or-None Response
Reflex arc (major parts & functions)
Withdrawal Reflex
- The response to touching something painful; sensory neurons, interneurons, and motor neurons
Synapse
is a junction between 2 communicating neurons
Patellar (knee-jerk) Reflex
- Helps maintain upright posture
Neural Pathways, the simplest of which is a
reflex arc
Receptors
- End of dendrites
Compare & contrast the ANS
Portion of the PNS that functions constantly and independently, without conscious effort.
ANS neurons are all
motor neurons
Sympathetic division:
active in conditions of stress or emergency (fight or flight)
Parasympathetic division:
active under normal, restful conditions (rest and digest).
Spinal nerves
31 pairs
of spinal nerves;
Except
the
first pair,
all are
mixed nerves
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
a sensory dorsal root, and a motor ventral
root