KPER 1500: Nervous System Divisions

• KPER 1500 Foundations of Physical Activity and Kinesiology, Week 3, Lecture 10 covers the Nervous System

Nervous System Divisions

• The nervous system is divided into the Central Nervous System (CNS) and Peripheral Nervous System (PNS).
• The CNS includes the brain, spinal cord, and interneurons.
• The PNS includes motor and sensory neurons, as well as the autonomic, somatic, and enteric nervous systems.
• The autonomic nervous system controls subconscious activities, and is divided into the parasympathetic (rest and digest) and sympathetic (fight or flight) systems.
• The somatic nervous system controls conscious activities.
• The enteric nervous system controls digestion.
• Efferent signals are sent from the CNS to the PNS.
• Afferent signals are sent from the PNS to the CNS.

Sensory Information Processing

• Sensory integration combines information from multiple senses to create a unified perception.
• Sensory receptors pick up information from the environment.
• Signals travel through afferent neural pathways to the spinal cord.
• Basic sensory integration and reflex actions occur in the spinal cord.
• The brain integrates sensory inputs through the thalamus and then the cerebral cortex.

Thalamus

• The thalamus serves as a major "relay station" for all synaptic input.
• It contributes to crude awareness of sensation.

Cerebral Cortex

• Responsible for complex mental functions such as thinking, memory, creativity, decision-making, and language.
• It interprets conscious sensory information.
• It's responsible for the voluntary control of movement.

Motor Information Processing

• The brain interprets sensory information to produce a motor response.
• Information is processed by the motor cortex, including the primary, premotor (movement planning), and supplementary motor areas.
• Stimulus identification, response selection, and response programming are part of the process which includes movement initiation + Basal Ganglia = Processing Loop.
• The cerebellum monitors movements.
• Efferent messages are sent down the spinal cord to activate muscles.

Motor Cortex

• The motor cortex sends messages to the spinal cord to direct movement.
• Motor programs are stored within the motor cortex.
• The basal ganglia influence correct selection of motor programs.

Basal Ganglia

• The basal ganglia plays a central role in motor control.
• It initiates voluntary movement.
• It coordinates slow voluntary movement.
• It acts to inhibit muscle tone.

Cerebellum

• The cerebellum monitors ongoing movements for error detection and correction to 'fine-tune' movements.
• It assists in the maintenance of balance and muscle tone.
• It contributes to the coordination of voluntary movement.
• The cerebellum provides spatial navigation.

Emotional Processing and Personality

• Emotional processing and personality relies on the interaction between the limbic system and pre-frontal cortex.

Prefrontal Cortex

• The prefrontal cortex is responsible for processing of emotional stimuli.
• It modulates emotional responses.
• It has conscious control over emotions.
• It integrates emotions with personality traits.

Limbic System

• The limbic system is the emotional centre of the brain which includes motivation and memory.
• The hippocampus is for decision making and memory development.
• The amygdala triggers fight or flight responses.

Hypothalamus

• The hypothalamus assists in body temperature maintenance.
• It helps control thirst and food intake.
• It regulates urine output by controlling fluid balance.
• It contributes to the control of emotional behavior including mood: Amygdala detects a threat and sends a signal to the hypothalamus, followed by the hypothalamus activating the sympathetic nervous system, and the hypothalamus sending signals to the adrenal glands, which are located on top of the kidneys and which then release adrenaline into the bloodstream.

Brain Stem

• The brain stem (midbrain, pons, medulla oblongata) connects the brain and spinal cord.
• It controls vital life functions such as cardiovascular, respiratory, and digestive regulation.
• It influences the arousal of the cerebral cortex.
• It regulates sleep and wake cycles.
• It regulates certain muscular reflexes associated with posture and controls movement during sleep.

CNS - Spinal Cord

• The spinal cord's role is for integration and relay of motor and sensory information.
• It controls reflexes and coordination of locomotion.
• It begins at the medulla oblongata in the brain.
• It continues through the vertebral cavity, where it separates in the lumbar region into a bundle of nerves called the cauda equina, sacrum, and coccyx.

Peripheral Nervous System - Neurons

• The soma is also know as the cell body.
• Dendrites carry messages towards the soma.
• Axons carry nerve impulses away from the soma.
• A synapse is the space between neurons.
• Neurotransmitters are signalling molecules secreted by a neuron to bridge the synapse space.

Characteristics of a Neuron

• Irritability (or excitability) refers to the ability of the neuron to respond to stimulation, which can facilitate or inhibit action and has an all or none threshold of activation.
• Conductivity refers to the ability of the neuron to send information to other structures.
• Myelin is a fatty substance that insulates the nerve impulse and increases the speed up to 50X.

Neuron Types

• Sensory neurons are afferent and carry signals to the CNS.
• Motor neurons are efferent and bring messages from the CNS to extremities.
• Mixed nerves contain both afferent and efferent neurons.

Functional Divisions of the PNS

• The Autonomic Nervous System includes the Sympathetic and Parasympathetic systems.
• The Sympathetic system facilitates fight or flight by increasing respiration and heart rate, releasing adrenaline and other hormones, and reducing digestion.
• The Parasympathetic system inhibits, e.g., decreases heart rate for rest and digest by countering the sympathetic system to bring the body to rest, increasing digestion, and eliminates waste.
• The Somatic Nervous System is the only consciously controlled part of the PNS and controls skeletal muscle.