The Nervous System - Midterm Master Set

Nervous system

Uses electrical impulses and chemical signals to maintain homeostasis

Sensory function

Detects internal and external stimuli

Integration

Processes and interprets sensory input

Motor function

Responds via muscles or glands

Neuron

Functional unit of nervous system

Dendrite

Receives signals toward cell body

Cell body (soma)

Contains nucleus and processes information

Axon

Conducts signals away from cell body

Axon terminal

Releases neurotransmitter

Axon hillock

Integration site where action potentials begin

Myelin sheath

Insulates axon and increases conduction speed

Nodes of Ranvier

Gaps in myelin that allow saltatory conduction

Sensory neuron (afferent)

Carries information toward CNS

Motor neuron (efferent)

Carries information away from CNS

Interneuron

Connects neurons within CNS

Glial cells

Support cells of nervous system

Oligodendrocytes

Produce myelin in CNS

Schwann cells

Produce myelin in PNS

Astrocytes

Maintain environment and blood-brain barrier

Microglia

Immune defense cells of CNS

Ependymal cells

Produce and circulate cerebrospinal fluid (CSF)

Membrane potential

Electrical difference across cell membrane

Resting membrane potential

Approximately -70 mV

Depolarization

Membrane becomes more positive

Repolarization

Membrane returns to negative

Sodium (Na+)

Major extracellular ion

Potassium (K+)

Major intracellular ion

Action potential

Rapid electrical signal along neuron

Threshold

Minimum stimulus needed to trigger AP

All-or-none principle

Action potential either occurs fully or not at all

Synapse

Junction between neurons

Presynaptic neuron

Sends signal

Postsynaptic neuron

Receives signal

Chemical synapse

Uses neurotransmitters

Electrical synapse

Direct ion flow between cells

Neurotransmitter

Chemical messenger between neurons

Brain

Control center of nervous system

Cerebrum

Higher thinking and conscious processing

Cerebellum

Coordination and balance

Brainstem

Controls basic life functions

Thalamus

Relays sensory information to cortex

Hypothalamus

Regulates temperature, hunger, hormones

Corpus callosum

Connects left and right hemispheres

Pons

Relays signals to cerebellum

Medulla oblongata

Controls breathing, heart rate, blood pressure

Meninges

Protective layers of CNS

Dura mater

Outer tough layer

Arachnoid mater

Middle layer

Pia mater

Inner delicate layer

Subarachnoid space

Contains cerebrospinal fluid

Cerebrospinal fluid (CSF)

Cushions brain and spinal cord and maintains chemical environment

Blood-brain barrier

Protects brain from harmful substances

Spinal cord

Conducts signals and reflexes

Reflex

Fast automatic response

Reflex arc

Pathway including receptor, sensory neuron, interneuron, motor neuron, effector

Dorsal root

Sensory input enters spinal cord

Ventral root

Motor output leaves spinal cord

Dorsal root ganglion

Contains sensory neuron cell bodies

Spinal nerves

31 pairs of mixed nerves

Stimulus

Environmental change detected by receptors

Sensation

Awareness of stimulus

Perception

Interpretation of stimulus

Sensory receptor

Detects stimulus

Transduction

Conversion of stimulus into electrical signal

Mechanoreceptor

Detects touch, pressure, vibration

Thermoreceptor

Detects temperature

Chemoreceptor

Detects chemicals such as CO2 or pH

Photoreceptor

Detects light

Nociceptor

Detects pain

Receptor potential

Change in membrane potential in response to stimulus

Adaptation

Decreased response to constant stimulus

Receptive field

Area monitored by a sensory receptor

Somatic sensation

Touch, temperature, pain, body position

Kinesthesis

Sense of body position and movement

Merkel discs

Slow adapting touch receptors

Meissner corpuscles

Fast adapting light touch receptors

Pacinian corpuscles

Detect deep pressure and vibration

Ruffini endings

Detect stretch

Pain

Perception of tissue damage

Referred pain

Pain felt in different location than source

Hyperalgesia

Increased sensitivity to pain

Analgesia

Pain relief

Cranial nerves

12 pairs of nerves from brain

Olfactory nerve (CN I)

Smell

Optic nerve (CN II)

Vision

Facial nerve (CN VII)

Taste anterior 2/3 of tongue

Glossopharyngeal nerve (CN IX)

Taste posterior 1/3 of tongue

Gustation

Sense of taste

Taste buds

Clusters of taste receptor cells

Taste types

Sweet, sour, salty, bitter, umami

Olfaction

Sense of smell

Olfactory receptors

Detect odor molecules

Olfactory bulb

Processes smell information

Pinna (auricle)

Collects sound waves

External auditory canal

Funnels sound to tympanic membrane

Tympanic membrane

Vibrates in response to sound

Ossicles

Malleus, incus, stapes transmit vibrations

Cochlea

Hearing organ containing hair cells

Semicircular canals

Detect rotational movement

Vestibule

Detects balance and position