Body Systems: Nervous

part i

What are the levels of organization in a multicellular organism?

Cells, tissues, organs, and organ systems

What are tissues?

Groups of similar cells that perform a single function

What is an organ?

A group of tissues that work together to perform a complex function

What is an organ system?

A group of organs that perform closely related functions

What is epithelial tissue?

Includes glands and tissues that cover interior and exterior body surfaces

What is connective tissue?

Provides support for the body and connects its parts

What do neurons do?

Transmits impulses throughout the body

What are muscles?

Enables the body to move (along with bones)

What is the frontal or coronal plane?

Divides the body into front (anterior) and back (posterior) regions

What is the median plane?

Divides the body into right and left regions

What is the horizontal plane?

Divides the body into a top and bottom half

What is the sagittal plane?

Any plane parallel to the frontal plane

What is the cerebrum responsible for?

Responsible for voluntary activities

What is the frontal lobe responsible for?

Reasoning, emotions, judgment, and voluntary movement

What is Occipital Lobe responsible for?

Vision and reading ability

What is the Parietal Lobe responsible for?

Sensory centers

What is the Temporal Lobe responsible for?

Centers of hearing and memory

What is the cerebellum responsible for?

Responsible for coordinated body movements

What is the corpus callosum responsible for?

Connects the right and left sides of the brain

What is the medulla oblongata responsible for?

Controls function of internal organs

What role does the nervous system play in the functions of the body?

Controls and coordinates functions throughout the body and responds to internal and external stimuli

What makes up the central nervous system?

Brain and spinal cord

What makes up the peripheral nervous system?

Nerve that connect to the rest of the body (from CNS)

What do sensory neurons do?

Transmits impulses from sense organs to CNS

What do motor neurons do?

Transmits impulses from CNS to muscles and glands

What is the somatic nervous system responsible for?

Reflexes and voluntary activities

What is the autonomic nervous system responsible for?

Involuntary activities, such as changing heart rate

What is a neuron?

Nerve cell that carries messages throughout the nervous system

What are the two sections of the nervous system?

PNS & CNS

What do interneurons do?

Connect sensory and motor neurons

Resting Membrane Potential

The electrical potential difference across the plasma membrane of a cell when it is in a non-excited state. Typically around -70mV in neurons, maintained by ion gradients and selective permeability to ions like K^+.

Depolarization

A change in a cell's membrane potential, making it more positive or less negative. In neurons, it is often caused by an influx of Na^+ ions, moving the membrane potential towards the threshold for an action potential.

Hyperpolarization

A change in a cell's membrane potential, making it more negative. It can be caused by efflux of K^+ or influx of Cl^−, and it reduces the likelihood of an action potential.

Threshold Potential

The critical level of depolarization (−55mV to -50mV in many neurons) that must be reached for an action potential to be initiated. At this point, voltage-gated sodium channels open rapidly.

Voltage-Gated Ion Channels

Ion channels in the plasma membrane that open or close in response to changes in the membrane potential. Crucial for generating action potentials, examples include voltage-gated Na^+ and K^+ channels.

Action Potential

A rapid, transient, all-or-none electrical signal conducted along an axon when the membrane potential reaches threshold; consists of depolarization and repolarization phases.

Sodium-Potassium Pump (Na^+/K^+ ATPase)

A transmembrane protein that uses ATP to actively transport Na^+ out of the cell and K^+ into the cell, maintaining the ion gradients necessary for the resting membrane potential and action potentials.

Refractory Period

A period following an action potential during which the neuron is either incapable of firing another action potential (absolute refractory period) or requires a stronger stimulus to do so (relative refractory period).

Absolute Refractory Period

The period immediately following the initiation of an action potential when another action potential cannot be triggered. This is primarily due to inactivated Na^+ channels.

Relative Refractory Period

The period following the absolute refractory period when a stronger-than-normal stimulus is required to initiate an action potential. This is due to the continued efflux of K^+ and hyperpolarization of the membrane.