Nervous System Flashcards
Functions of nervous system:
- Sensory input
- Integration
- Control of muscles and glands
- Mental activity
- Homeostasis
Main Divisions of the Nervous System:
- Central Nervous System (CNS): brain and spinal cord
- Peripheral Nervous System (PNS): all neurons outside CNS
Neuron Characteristics:
- Nerve cells
- Require oxygen and glucose
- Receive input, process input, and produce a response
Neuron Structures:
- Dendrite - receives stimulus from other neurons or sensory receptors
- Cell body - processes stimulus, contains a nucleus
- Axon - transmits stimulus to a gland, muscle, organ, or other neuron
Myelin Sheath
fatty, protective wrapping around axons
gaps in myelin sheath where action potentials develop
Nodes of Ranvier
jumping of action potentials
Saltatory conduction
disease of myelin sheath that causes loss of muscle function
Multiple sclerosis
Types of Neurons:
- Multipolar neuron - many dendrites and a single axon
- Bipolar neuron - one dendrite and one axon
- Pseudo-unipolar neuron - one axon and no dendrites
Neuroglia Characteristics:
- Supporting cells for neurons
- More numerous than neurons
- Can divide to produce more cells
5 types:
- Astrocytes
- Ependymal Cells
- Microglia
- Oligodendrocytes
- Schwann cells
- star-shaped
- most abundant
- form blood-brain barrier
Astrocytes
produce and circulate cerebrospinal fluid (CSF)
Ependymal Cells
help remove bacteria and cell debris from CNS
Microglia
produce myelin sheath in CNS
Oligodendrocytes
produce myelin sheath in PNS
Schwann cells
Organization of Nervous Tissue:
- Gray matter: - collection of dendrites and cell bodies
- White matter: - collection of axons and their myelin sheath
Produce myelin sheath:
CNS: Oligodendrocytes
PNS: Schwann cells
Collection of axons:
CNS: Nerve tracts
PNS: Nerves
Collection of cell bodies:
CNS: Nuclei
PNS: Ganglion
Resting Membrane Potential:
- Outside of cell is more + (Na+)
- Inside of cell is more – (K+)
-
Leak ion channels:
- always open
- K+ channels
-
Gated ion channels:
- closed until opened by specific signal
- Na+ channels
- “Electricity” that cause depolarization and repolarization
- Change resting membrane potential by activating gated ion channels
Action Potentials
If enough Na+ enters then ________ is reached and more Na+ channels open
threshold
Action potentials continue until Na+ channels close, K+ channels open, and ________ occurs
repolarization
where an axon attaches to a muscle, gland, organ, or other neuron
Synapse
involuntary response to a stimulus
Reflexes
path reflex travels
Reflex arc
Components of Reflex Arc:
1. Sensory receptors:
- pick up the stimulus
- in skin
2. Sensory (afferent) neurons:
send stimulus to interneurons in the spinal cord
3. Interneurons (Association) neuron:
- located in the CNS and connected to motor neurons
- process stimulus
4. Efferent (motor) neurons:
send a response to the effector
5. Effector:
muscle, gland, or organ
two or more neurons synapse the same neuron
Converging
axon from one neuron divides and synapses with more than one neuron
Diverging
Consists of brain and spinal cord
Central Nervous System
It includes nerves outside the brain and spinal cord
Peripheral Nervous System
Extends from foramen magnum to 2nd lumbar vertebra
Spinal Cord
Gray and White Matter in Spinal Cord:
Gray Matter:
center of the spinal cord
looks like the letter H or a butterfly
White Matter:
outside of the spinal cord
contains myelinated fibers
White Matter in Spinal Cord
- Contains 3 columns dorsal, ventral, and lateral columns
-
Ascending tracts:
axons that conduct action potentials toward the brain -
Descending tracts:
axons that conduct action potentials away from the brain
Gray Matter in Spinal Cord:
Posterior horns:
contain axons that synapse with interneurons
Anterior horns:
contain somatic neurons
Lateral horns:
contain autonomic neurons
Central canal:
fluid-filled space in the center of the cord
Arise along spinal cord from union of dorsal roots and ventral roots
Spinal Nerves
Originates from spinal nerves C1-4, it innervates muscles attached to the hyoid bone and neck
Cervical Plexus
Originates from spinal nerves C5-T1, it supplies nerves to the upper limb, shoulder, hand
Brachial Plexus
Originates from spinal nerves L1 to S4, it supplies nerves in the lower limbs
Lumbosacral Plexus
Fluid that bathes the brain and spinal cord
Cerebrospinal Fluid
Brainstem components:
- Medulla oblongata
- Pons
- Midbrain
component of the brainstem that regulates heart rate, blood vessel diameter, breathing, swallowing, vomiting, hiccupping, coughing, sneezing, balance
Medulla oblongata
component of the brainstem that regulates breathing, chewing, salivation, swallowing
Pons
component of the brainstem that coordinated the eye movement, pupil diameter, turning head toward noise
Midbrain
regulates cyclical motor function, respiration, walking, chewing, arousing, and maintaining consciousness regulates the sleep-wake cycle
Reticular Formation
Diencephalon:
- Located between the brainstem and cerebrum
Components:
* Thalamus - influences moods and detects pain
* Epithalamus - an emotional and visceral response to odors
* Hypothalamus - controls homeostasis, body temp, thirst, hunger, fear, rage, sexual emotions
