Nervous Tissue

Afferent

Carries sensory info from peripheral nervous system sensory receptors to central nervous system.

Efferent

Carries motor commands from central nervous system to peripheral nervous system.

Functions of the nervous system

Sensory input, integration, motor output.

Sensory neurons

Transmits sensory information from sensory receptors towards CNS, afferent, located outside of the CNS.

Motor neurons

Transmits signals from CNS to muscles/glands for a response, located inside CNS.

Receptors

Structures/proteins that detect changes or respond to stimuli, usually proteins that change shape.

Neurotransmitter

A chemical messenger that transmits signals across a synapse.

Synaptic cleft

The gap between two neurons or a neuron and cell where neurotransmitters cross.

Ependymal cells

CNS cells that line the central canal of spinal cord and ventricles of the brain to secrete and circulate CSF.

Astrocytes

CNS cells that maintain the blood-brain barrier to protect the brain and support neurons.

Oligodendrocytes

CNS cells that enhance signal transmission by forming myelin sheaths around axons.

Microglia

Immune cells of CNS that clean up debris, waste products, and pathogens.

Satellite cells

PNS cells that surround and support ganglia by regulating their environment.

Schwann cells

PNS cells that form the myelin sheath around nerves.

Myelination

Increases conduction speed by insulating nerves to block leakage channels.

Gray matter

Unmyelinated areas of the CNS.

White matter

Regions of the CNS that contain myelinated nerves.

Action potential

An all-or-nothing response in neurons that occurs when a stimulus reaches a certain threshold.

Resting potential

The charge of a neuron at rest, typically -70mV.

Na+, K+ ATPase

A pump that uses ATP to move sodium out of and potassium into the cell against their gradients.

Continuous conduction

The conduction method in unmyelinated neurons involving closely spaced voltage-gated channels.

Saltatory conduction

The conduction method in myelinated neurons where the action potential jumps between nodes of Ranvier.

Depolarization

A change in membrane potential that makes it less negative due to Na+ influx.

Hyperpolarization

A change in membrane potential that makes it more negative due to K+ efflux.

Somatic Nervous System (SNS)

Part of the PNS that controls voluntary movements of skeletal muscles.

Autonomic Nervous System (ANS)

Part of the PNS that controls involuntary activities like heart rate and digestion.

Electrical synapse

Fast, bidirectional signal transmission between cells through gap junctions.

Chemical synapse

Slower, unidirectional signal transmission involving neurotransmitters.

Graded potential

A temporary change in charge of a cell involving ligand-gated and mechanically-gated channels.

Fiber types

A- fastest and myelinated, B- intermediate and myelinated, C- slowest and unmyelinated.

Leakage channels

Always open channels in nerve cells, with more K+ than Na+ channels.

Chemically-gated channels

Open in the presence of certain chemicals (ligands), such as ACh.

Voltage-gated channels

Respond to changes in membrane potential and open at specific voltages.

Mechanically gated channels

Respond to membrane distortion, found in sensory receptors.

Permeability and channel relationship

Directly proportional; more open channels increase permeability.

Location of voltage-gated channels

Found in neural axons, skeletal muscle sarcolemma, and cardiac muscles.

Myelin degradation effect

Communication stops, potentially leading to death due to respiratory failure.

Adrenoleukodystrophy (ADL)

An X-linked recessive disorder that affects fat metabolism and leads to myelin sheath destruction.

when ACh binds to the heart, what is the response?

it is inhibitory, slows down the heart rate