Nervous System: Brain and Spinal Cord

Nervous System Overview

• The tutor for this presentation is Debbie Hemington, module BMS

Learning Outcomes

• At the end of this session you will be able to describe the 2 parts of the nervous system
• You will also be able to list the key features of the human brain and spinal cord, the main areas of the brain and their function, the functions of cerebrospinal fluid, and the groups of spinal nerves

Assessment

• Assessment will be formative, with short answers and MCQ
• Assessment will also be summative, with end of module exams

The Central Nervous System

• Includes the brain and spinal cord

Brain

• Weighs approximately 1.4 kg and is located in the cranial cavity
• Made up of the cerebrum, thalamus, hypothalamus, midbrain, pons, medulla oblongata, and cerebellum

Cerebrum

• The largest part of the brain
• Has 3 main functional areas associated with mental activities like memory, and thinking
• Sensory perception includes perception of pain, temperature, and touch
• Initiates and controls voluntary muscle contraction

The Cerebrum

• The cerebral cortex is highly wrinkled
• These folds increase the surface area of the brain and the number of neurons
• A deep furrow divides the cerebrum into left and right hemispheres
• The corpus callosum is a bundle of axons that connects these two hemispheres

Thalamus

• A small structure
• Sensory receptors in skin and viscera send info about touch, pain and temperature here
• Input from the special sense organs is processed in basic form here too
• Thought to be involved in arousal and the processing of some emotions/complex reflexes

Hypothalamus

• It is situated within the cerebrum and attached to the pituitary gland
• The hypothalamus controls the output of hormones and effectors of the autonomic nervous system
• It manages emotional reactions, hunger, thirst, body temperature, and biological clocks

Midbrain

• Consists of nuclei and nerve fibres
• Connects the cerebrum with the lower parts of the brain and spinal cord
• Nuclei act as relay stations for ascending and descending nerve fibres
• Has important roles in auditory and visual reflexes

Pons

• Contains nerve fibres, that form a bridge between the two hemispheres of the cerebrum
• Processes information from several of the cranial nerves

Medulla Oblongata

• Continuous with the spinal cord
• It controls cardiovascular and respiratory centers
• It controls reflex centers for coughing, vomiting, sneezing, and swallowing

Spinal Cord

• Nerves conveying impulses from the brain to various organs and tissues descend through it
• Starts in the medulla oblongata and descends through the spinal column

Spinal Chord

• Elongated and almost cylindrical with the CNS
• Suspended in the vertebral canal
• Surrounded by meninges and cerebro-spinal fluid
• Approximately the thickness of a little finger and 45cm long

Cerebrospinal Fluid

• A clear, colourless fluid that occupies the subarachnoid space in the brain
• Cushions the cortex, is renewed 4 times daily and contains proteins, glucose and lymphocytes

Functions of Cerebrospinal Fluid

• Protection
• Buoyancy
• Exrection of waste products
• Endocrine medium for the brain

Protection

• Cerebrospinal fluid (CSF) protects the brain by 'buffering' the brain
• This lessens the impact when there is a blow to the head

Buoyancy

• Because the brain is immersed in fluid, its weight is reduced
• The weight is reduced from about 1400g to about 50g
• This reduces the pressure at the base of the brain

Excretion of Waste Products

• One-way flow from the Cerebrospinal fluid (CSF) to the blood removes harmful metabolites, drugs and other substances from the brain

Endocrine Medium for the Brain

• The Cerebrospinal fluid (CSF) serves to transport hormones to certain areas of the brain
• Hormones released into the CSF can be carried to remote sites of the brain

Peripheral Nervous System

• Made up of cranial nerves, spinal nerves and peripheral nerves
• It contains sensory neurons, and motor neurons

Peripheral Nervous System Breakdown

• The nervous system comprises the central and peripheral systems
• The peripheral is further divided into somatic (voluntary) autonomic (involuntary) systems
• The autonomic system is then divided into the sympathetic (fight or flight) and parasympathetic (rest and digest) systems

Autonomic System

• The sympathetic system activates the "fight or flight" response during a threat
• The parasympathetic system restores the body to a state of calm, the "rest & digest" phase

Parasympathetic Nerves

• "Rest & digest" / "Feed & breed"
• Constrict pupils, Slow heartbeat, Constrict airways
• Stimulate stomach activity, inhibit glucose release, and stimulate sexual arousal in both men and women

Sympathetic Nerves

• "Fight or flight"
• Dilate pupils, Increase heartbeat, Relax airways
• Inhibit stomach activity, stimulate glucose release, secrete adrenaline
• Encourage ejaculation and vaginal contractions

Cranial Nerves

• Sensory fibres, motor fibres and intermediate nerves

Spinal Nerves

• The spinal cord consists of cervical vertebrae (C1-C8), thoracic vertebrea (T1-T12), lumber vertebrae (L1-L5), sacrum and coccyx

Peripheral nerves

• Include brainstem, spinal cord, brachial plexus, lumbar plexus sacral plexus and pudendal nerve

Overview of the human nervous system, including the brain and spinal cord. Covers the major brain regions such as the cerebrum, thalamus, and cerebellum, along with their functions. Also explores the role of cerebrospinal fluid and spinal nerves.