Nervous System Overview and Neuron Parts

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.