Nervous System Overview and Neuron Parts

Study Notes

Nervous System Overview

The nervous system coordinates and regulates feedback mechanisms to maintain homeostasis.
Learning objectives include understanding nervous system functions, identifying structural and functional units, describing the various divisions, and distinguishing between sympathetic and parasympathetic systems.
The nervous system is composed of the central nervous system (CNS) and the peripheral nervous system (PNS).

Parts of a Neuron

Dendrites: Receive signals from other cells.
Cell body: Organizes and keeps the cell functioning.
Cell membrane: Protects the cell.
Axon hillock: Generates impulses in the neuron.
Axon: Transfers signals to other cells and organs.
Myelin sheath: Increases the speed of the signal.
Axon terminal: Forms junctions with other cells.
Node of Ranvier: Allows diffusion of ions.
Schwann cell: Produces the myelin sheath.
Nucleus: Controls the entire neuron.

Neuron Classification

Sensory (or afferent) neurons: Carry impulses from sense organs to the brain and spinal cord.
Motor (or efferent) neurons: Carry impulses from the brain and spinal cord to muscles.
Association neurons: Located in the CNS, analyze and interpret data or impulses.

Central Nervous System (CNS)

Serves as the main processing center of the nervous system.
Parts include the brain (cerebrum, cerebellum, brain stem) and the spinal cord.

Brain

Cerebrum: Responsible for sensing, thinking, emotions, and voluntary movements.
Cerebellum: Controls balance and fine muscle movements.
Brain stem: Controls bodily functions like breathing, circulation, and sleep.
Limbic System: Responsible for basic biological needs.

Four Lobes of the Brain

Frontal lobe: Responsible for cognitive functions and movement.
Parietal lobe: Responsible for processing touch, pain, temperature, and movement.
Occipital lobe: Responsible for vision.
Temporal lobe: Responsible for speech, hearing, and memory.

Spinal Cord

An elongated bundle of neurons; a channel for signals between the brain and the majority of the body parts.
Divided into cervical, thoracic, lumbar, and sacral regions.

Peripheral Nervous System (PNS)

Connects the CNS to organs and limbs, is categorized into:
- Somatic system: Processes sensory information and controls voluntary muscle movements. Also controls reflexes.
- Autonomic system: Regulates involuntary activities like heart function, smooth muscle control, and other internal organs (intestines, bladder, uterus).

Autonomic Nervous System (ANS)

- Sympathetic ("fight or flight"): Stimulates the body to use energy and drive automatic responses during stress.
- Parasympathetic ("rest and digest"): Conserves energy, regulates automatic bodily functions during rest.

Homeostasis and the Body Systems

The nervous system and endocrine system work together to maintain homeostasis.
Homeostasis is maintained by regulating body temperature, blood pressure, pH, and glucose concentration.
Various body systems alongside the nervous system work together to control homeostasis.

Feedback Mechanisms

Negative feedback: A control system to reduce or minimize change in the body, maintains homeostasis and set point.
Positive feedback: Increases the rate of a process, is the opposite of negative feedback. Examples include milk production, labor contractions, and blood clotting.

Activity Recommendations

Examples of activities include categorizing movements (somatic or autonomic), filling in graphic organizers, and explaining how systems maintain homeostasis.