Neuroscience Chapter: Brain Anatomy Quiz

Human Physiology 2 - Course Information

• Course name: Human Physiology 2
• Course code: PHYG 13383D
• Lectures: Mondays and Wednesdays, 12-2 PM

Evaluation Plan

• Assignment: 10%
• Quizzes (6): 15%
• Midterm Exam 1: 25%
• Midterm Exam 2: 25%
• Final Exam: 25%
• Total: 100%

Lecture 1: Organization of the Nervous System

• Textbook: Sherwood & Ward 5th Edition, Chapters 3, 4, 5
• Topic focus: The organization of the nervous system

Objectives (Knowledge)

• Levels of organization of the nervous system
• Distinguishing structurally and functionally between neurons and neuroglia
• Mechanisms of brain homeostasis maintenance
• Review of gross anatomical divisions of the brain (BIOL 19201)

Objectives (Application)

• Describe how brain homeostasis can be altered
• Correlate pathophysiological changes in brain tissue with obstructions in cerebral blood flow

Major Structures within the Brain and Organization of the Nervous System

• Central nervous system (CNS): Includes the brain and spinal cord, responsible for integrative and control center functions
• Peripheral nervous system (PNS): Includes cranial nerves and spinal nerves, responsible for communication between the CNS and the rest of the body
• Sensory (afferent) division: Conducts impulses from receptors to the CNS
• Motor (efferent) division: Conducts impulses from the CNS to effectors (muscles and glands)
• Autonomic nervous system (ANS): Responsible for involuntary control of visceral functions
• Somatic nervous system: Responsible for voluntary control of skeletal muscles
• Sympathetic division: Mobilizes the body during emergencies
• Parasympathetic division: Conserves energy and promotes non-emergency functions and conditions

Major Structures within the Brain:

• Cerebrum: Largest part, with four lobes (frontal, parietal, temporal, occipital) and three basic regions: cerebral cortex, cerebral white matter, and basal nuclei; 83% of brain mass
• Diencephalon: Contains the thalamus (relay center for sensory input) and hypothalamus (homeostatic control center)
• Brain Stem: Connects the brain to the spinal cord; includes midbrain, pons, and medulla oblongata; responsible for integration of motor output and sensory perception.
• Cerebellum: Posterior to the brain stem; monitors and enhances motor system functions.

Specific details

• Cerebral Cortex: Superficial gray matter; critical for sensory perception, memory, communication, understanding voluntary movement; each hemisphere largely acts contralateral; Lateralization
• Cerebral White Matter: Responsible for communication between different brain areas
• Commissures: Connect areas between the two cerebral hemispheres. Enable the hemispheres to work as a whole
• Association Fibers: Connect different parts of the same hemisphere
• Projection Fibers: Connect the cortex to the diencephalon and other structures.
• Basal Nuclei: Located deep within cerebral white matter, crucial for control of movement, particularly through inhibition of muscle tone.
• Thalamus: Relay station for sensory input, including crude sensation awareness and role in motor control
• Hypothalamus: Central for homeostatic function (temperature regulation, thirst, urine control, hunger), plays a vital role in the sleep-wake cycle
• Specialized structures: Broca’s area for speech; Wernicke’s for language comprehension.

Quiz Questions

• The brain and spinal cord are part of the nervous system.
• Four brain lobes: frontal, parietal, temporal, occipital.
• An area of the brain involved in motor control: primary motor cortex, premotor cortex, frontal eye field
• A structure of the diencephalon: thalamus, hypothalamus
• A structure of the brain stem: pons, medulla oblongata, midbrain
• Sensory neurons enter the spinal cord through the dorsal horn.
• Direction of afferent neuron information: toward the brain.

Cells of the Nervous System

• Neurons: Highly specialized cells responsible for transmitting nerve impulses
  • Dendrites: Carry impulses toward the cell body.
  • Axons: Conduct impulses away from the cell body.
• Supporting Cells (Glial): Do not participate directly in synaptic interactions, but are supportive in nature. They are more numerous than neurons (~90% of nervous tissue).

Neuron Action Potential and Graded Potentials

• Action potential (AP): Sudden and rapid changes in membrane permeability caused by ion channels opening and closing; propagated as an electrical current to trigger chemical responses (e.g., neurotransmitter release at synapses)
• Graded potentials: Small, localized changes in membrane potential; crucial for initiating action potentials; includes EPSPs (excitatory postsynaptic potentials) and IPSPs (inhibitory postsynaptic potentials)
• Sequence of events:

1. Presynaptic neuron releases neurotransmitters
2. Neurotransmitters bind to postsynaptic receptors
3. Ion channels open or close, leading to EPSPs or IPSPs.
4. Spatial and temporal summation of graded potentials lead to the generation of action potentials.

Neurotransmitters and Neuromodulators

• Neurotransmitters: Chemical messengers that carry signals between neurons. Examples: acetylcholine, norepinephrine, dopamine, glutamate, GABA.
• Neuromodulators: Chemical messengers influencing the strength or transmission of neurotransmitter signals. Examples include: serotonin, altering the sensitivity of the postsynaptic membrane to neurotransmitters
  • SSRIs (selective serotonin reuptake inhibitors) prevent the reabsorption of serotonin, leading to more prolonged effects of serotonin
  • MAOIs (monoamine oxidase inhibitors) prevent the breakdown of norepinephrine, dopamine, and serotonin, prolonging their effect

Maintenance of CNS Homeostasis

• Meninges: Protective membranes surrounding the CNS. Composed of the Dura Mater, Arachnoid Mater, and Pia Mater
• Blood-Brain Barrier (BBB): Structures that control the passage of substances from the blood into the CNS.
• Cerebrospinal Fluid (CSF): Protective fluid surrounding the brain and spinal cord.
• Blood Supply: Provides adequate nutrients to maintain normal neuronal and glial functions. Maintaining sufficient blood flow is crucial for the CNS.
• Clinical Case: An example of epidural hemorrhage impacting CNS homeostasis. (Describes symptoms)

Glial Cells-Supporting Cells of the Nervous System

• Astrocytes: Most abundant glial cells, provide structural support, regulate the chemical environment around neurons, and assist in nutrient and waste exchange
• Microglia: Immune cells of the CNS that act as phagocytes to remove cellular debris and infectious agents
• Ependymal cells: Line ventricles and central canal of the spinal cord, and help circulate cerebrospinal fluid (CSF)
• Oligodendrocytes: Form myelin sheaths around axons in the CNS.
• Satellite cells: Surround neuron cell bodies in the PNS, providing support and protection
• Schwann cells: Form myelin sheaths around axons in the PNS.

Additional Information

• The presentation also includes images and diagrams of the listed components which aid in visualization and understanding.