Neuroscience Quiz on Nervous System Functions

Canine Brain Anatomy

• Meninges are protective membranes covering the brain and spinal cord.
• Canine brains have specific regions related to behaviour, including chew toy discrimination, "play," responses to abandonment, and hyperactivity.

Learning Objectives

• Key anatomical structures of the CNS, including spinal cord endings, CNS membranes, cerebrospinal fluid (CSF) processes, and access points to epidural and subarachnoid spaces.

Central Nervous System Overview

• Components include the brain, spinal cord, and peripheral nervous system (PNS), further divided into sensory and motor systems.
• Protected by the cranial cavity and vertebral canal.

Spinal Cord and Cauda Equina

• Spinal cord ends at the lumbosacral junction.
• Cauda equina consists of spinal nerves extending past L7.
• Nerve root compression can cause pain, reduced tail wagging, defecation difficulty, and hind limb weakness.

Cauda Equina Syndrome (CES)

• Causes include lumbosacral junction compression (e.g., disc degeneration, arthritis).
• Symptoms include lower back pain, behavioral changes (like low tail carriage), and urinary/fecal incontinence in severe cases.
• Diagnosis involves neurologic exam, spinal palpation, and radiographs.
• Treatment typically involves conservative measures (rest and pain meds) or surgery (dorsal laminectomy) for severe cases.

Meninges and Spinal Membranes

• Dura mater is the outermost, thickest layer fused to the cranial cavity periosteum.
• Arachnoid mater is attached to the dura, containing blood vessels.
• Pia mater is the innermost layer, following brain gyri and sulci, involved in CSF production.
• Brain membranes are completed by the periosteum that lines the vertebral canal and skull.

Cerebrospinal Fluid (CSF) Functions

• Shock absorption, protecting the brain during movement.
• Maintains consistent intracranial pressure.
• Provides nutrition (glucose, proteins).
• Removes waste through circulation.
• Regulates brain and spinal temperature.
• Contains immune cells for pathogen monitoring.

Brain Hemisphere Control

• Right brain controls left body, and vice versa.
• Nerve impulse pathways cross, illustrating brain function lateralization.

Role of the Nervous System

• Controls and coordinates body functions (thinking, feeling, movement).
• Essential for survival and environmental stimulus response.

Environmental Interaction

• Detection, integration, and response to environment are crucial nervous system functions.
• Considered the most intricate body system.

Nervous System Functions

• Sensory function involves sensory receptors monitoring changes (internal/external).
• Integrative function processes and interprets sensory input, determining actions.
• Motor function transmits information to effectors (muscles, glands, organs).

Simplified Neural Circuit

• Receptor–effector pathway comprises skin receptor, sensory neuron, interneuron, motor neuron, and striated muscle effector.

Nervous System Subdivisions

• Central nervous system (CNS) includes brain and spinal cord.
• Peripheral nervous system (PNS) comprises cranial and spinal nerves, further divided into afferent and efferent divisions.

Peripheral Nervous System (PNS) Functional Divisions

• Afferent division: Conducts impulses toward the CNS from sensory receptors.
• Efferent division: Carries impulses away from CNS to effectors.

Somatic vs. Visceral Systems

• Somatic system involves sensory and motor functions related to external environment.
• Visceral system includes sensory and motor functions related to internal organs; part of the autonomic nervous system (ANS).

Autonomic Nervous System

• The ANS controls involuntary functions like blood pressure, heart rate, and digestion.
• Divided into sympathetic and parasympathetic divisions.

Somatic System

• Involves voluntary movements and sensory functions related to external stimuli.

Visceral System

• Involves sensory and motor functions regarding internal organs.
• Part of the ANS.

Autonomic Nervous System Parts

• Sympathetic: Mobilizes body systems during stress or activity ("fight or flight").
• Parasympathetic: Controls and conserves energy during rest.

Nervous System Summary

• CNS is the control center (brain and spinal cord).
• PNS are communication lines (cranial and spinal nerves).
• Key functions include sensory and motor transmissions (afferent and efferent).

Neuron Anatomy and Functions

• The basic building blocks of the nervous system.
• Dendrites receive input, cell body processes, axon transmits signals.

Spinal Cord Anatomy

• White matter contains myelinated axons.
• Gray matter comprises neuron cell bodies.
• Dorsal and ventral roots connect sensory and motor pathways.

Cranial Nerves

• Cranial nerves are nerves in the head. (I-XII).

Peripheral Nervous System Overview

• The PNS consists of nerves, ganglia, and plexi outside the CNS.
• Peripheral nerves consist of 33 spinal nerves (8 cervical, 13 thoracic, 7 lumbar, 3 sacral, 5 caudal).

Rami and Their Functions

• Spinal nerve branches (dorsal, ventral, and communicans) carry sensory and motor signals.
• Dorsal rami serve structures deep to the vertebrae.
• Ventral rami supply other body regions.

Nerve Plexi

• A network formed from branched nerves; ensuring comprehensive body innervation.

Revisiting CNS and PNS

• The CNS consists of the brain and spinal cord.
• The PNS contains nerves outside CNS (cranial and spinal).

Motor Subdivision of PNS

• Somatic: Voluntary muscle innervation via single neurons.
• Visceral: Involuntary tissue innervation via two neurons.

Synapses

• Synapses are points where neurons connect and transmit signals.

Autonomic Nervous System

• Responsible for involuntary processes (e.g., digestion, respiration).
• Two-neuron system for target organ activation.
• Sympathetic and parasympathetic divisions for often opposing effects.

Autonomic Nervous System - Two Neuron System

• Preganglionic neuron originates in CNS, connecting to a ganglion neuron.
• Postganglionic neuron in ganglion, innervates target organs (smooth muscle, cardiac muscle, glands).

Sympathetic vs Parasympathetic

• Sympathetic ("fight or flight"): Pupils dilate, inhibit salivation, increased heart rate, and airway dilation.
• Parasympathetic ("rest and digest"): Pupils constrict, stimulate salivation, reduced heart rate, and increased digestive processes.

Recap of Autonomic Systems

• Summarizes the roles of nervous system divisions.
• Highlights the crucial relationship between PsNS and SNS in maintaining homeostasis.

Sympathetic Nervous System

• Centers around the "fight-or-flight" response, triggering various processes for dealing with stress.
• Neuroanatomy involves preganglionic neurons originating in thoracolumbar regions, with postganglionic neurons residing in cervical, thoracic, or abdominal ganglia.

Reflex Arc

• Consists of receptors, sensory neurons, integration centre, motor neurons, and effectors.
• Somatic reflex involves skeletal muscles; autonomic reflex involves smooth muscles and glands.

Types of Cells in the Nervous System

• Neurons (excitable cells handling information processing).
• Neuroglia (supporting cells, for nerve cell maintenance and nourishment etc.).

Neuron Classifications

• Sensory (afferent) neurons carry sensory information to the CNS.
• Interneurons connect sensory and motor neurons within the CNS.
• Motor (efferent) neurons transmit signals from the CNS to effectors (muscles, glands).

Structural Classifications

• Unipolar neurons: single axon with peripheral and central branches.
• Bipolar neurons: Two processes (axon and dendrite).
• Multipolar neurons: Single axon and multiple dendrites (most common).

Neuron Anatomy

• Dendrites receive signals.
• Cell body integrates signals.
• Axon transmits signals.

Myelin and its Functions

• Myelin sheath formed by Schwann cells (PNS) or oligodendrocytes (CNS).
• Acts as insulation to speed up electrical signal conduction.
• Nodes of Ranvier are gaps in myelin that help promote rapid signal transmission.

Membrane Potential and Action Potentials

• Resting membrane potential: Electrical potential difference across the plasma membrane at rest.
• Action potential: Rapid changes in membrane potential (triggered by stimulus).
• Neurotransmitter release is at the synapse (via exocytosis when action potential reaches axon terminals).

Summary of Action Potential Stages (Depolarization, Repolarization, Hyperpolarization, Propagation)

• Provides an overview of electrical signal propagation along neuron axon.