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Questions and Answers
What is the primary function of the pons in the nervous system?
Which of the following statements about the spinal cord is true?
What does cerebrospinal fluid (CSF) NOT do?
How does cerebrospinal fluid contribute to the brain's buoyancy?
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What role does the medulla oblongata play in the nervous system?
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What is a primary characteristic of the peripheral nervous system?
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Which of the following best describes the sympathetic nervous system's function?
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Which of the following is NOT a function of cerebrospinal fluid?
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What is the largest part of the brain?
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Which structure connects the two hemispheres of the cerebrum?
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What role does the hypothalamus primarily play?
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Which function is primarily associated with the cerebrum?
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What is the primary function of the thalamus?
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What significant feature increases the efficiency of the cerebral cortex?
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What is one of the main functions of the midbrain?
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What are the two divisions of the nervous system?
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Which cells are primarily involved in the insulation of axons in the peripheral nervous system?
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What is the primary function of Dendrites?
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What is a synapse?
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What role do astrocytes play in the nervous system?
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Efferent impulses travel towards the brain.
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What is the function of the hypothalamus?
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The ___ is a bundle of axons connecting the left and right hemispheres of the brain.
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What is the role of the thalamus in the brain?
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What does the Pons contain?
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What does the Medulla Oblongata control?
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What is the primary function of the Cerebellum?
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How long is the spinal cord in adults?
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Cerebrospinal fluid (CSF) occupies the subarachnoid space.
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What is the role of the sympathetic nervous system?
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Which system is responsible for restoring the body to a state of calm?
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The spinal nerves consist of ___ pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
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Study Notes
The Central Nervous System
- The brain weighs approximately 1.4kg and is located within the cranial cavity.
- The brain comprises the cerebrum, thalamus, hypothalamus, midbrain, pons, medulla oblongata, and cerebellum.
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Cerebrum:
- It is the largest part of the brain.
- It has three main functional areas associated with mental activities, sensory perception, and voluntary muscle contraction.
- Mental activities include memory, intelligence, problem-solving, reflection, judgment, thinking, reasoning, initiative, inhibition, moral sense of responsibility, and learning.
- Sensory perception includes the perception of pain, temperature, and touch.
- The cerebral cortex is highly wrinkled, increasing the surface area and the number of neurons within the brain.
- A deep furrow divides the cerebrum into two halves, the left and right hemispheres, connected by the corpus callosum, a bundle of axons.
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Thalamus:
- It is a small structure that receives information about touch, pain, and temperature from sensory receptors in the skin and viscera.
- Input from special sense organs travels to the thalamus for basic perception.
- The thalamus is believed to be involved in arousal and processing some emotions and complex reflexes.
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Hypothalamus:
- It is situated within the cerebrum and attached to the pituitary gland.
- It controls the output of hormones and the effectors of the autonomic nervous system, including emotional reactions, hunger and thirst, body temperature, and biological clocks.
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Midbrain:
- It contains nuclei and nerve fibers connecting the cerebrum to lower parts of the brain and spinal cord.
- These nuclei act as relay stations for ascending and descending nerve fibers and play important roles in auditory and visual reflexes.
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Pons:
- It contains nerve fibers that act as a bridge between the two hemispheres of the cerebrum.
- It processes information from several cranial nerves.
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Medulla Oblongata:
- It is continuous with the spinal cord.
- It controls effectors, including the cardiovascular center, respiratory center, and reflex centers for coughing, vomiting, sneezing, and swallowing.
Spinal Cord
- The spinal cord is an elongated, almost cylindrical part of the CNS suspended in the vertebral canal.
- It is surrounded by meninges and cerebrospinal fluid, is approximately the thickness of a little finger, and is about 45 centimeters long.
- Nerves conveying impulses from the brain to various organs and tissues descend through the spinal cord.
- It starts in the medulla oblongata and descends through the spinal column.
Cerebrospinal Fluid (CFS)
- It is a clear, colorless fluid that occupies the subarachnoid space of the brain.
- It acts as a cushion or buffer for the cortex and is renewed four times daily.
- CFS contains proteins, glucose, and lymphocytes.
Functions of Cerebrospinal Fluid
- Protection: CFS "buffers" the brain, lessening the impact of blows to the head.
- Buoyancy: Due to immersion in fluid, the net weight of the brain is reduced from approximately 1400g to about 50g, decreasing the pressure at the base of the brain.
- Excretion of Waste Products: The one-way flow from the CSF to the blood removes potentially harmful metabolites, drugs, and other substances from the brain.
- Endocrine Medium for the Brain: CSF transports hormones to certain areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they can act.
The Peripheral Nervous System (PNS)
- This comprises the nerves that branch out from the brain and spinal cord.
- This system connects the CNS to the rest of the body.
Autonomic Nervous System
- Sympathetic Nervous System: This system activates the "fight or flight" response during a threat or perceived danger, necessary for short-term survival.
- Parasympathetic Nervous System: This system restores the body to a state of calm, the "rest and digest" phase, necessary for long-term survival.
The Nervous System
- The nervous system detects and responds to changes both internally and externally within the body.
- It is responsible for controlling important body functions alongside the endocrine system.
- The nervous system maintains homeostasis.
- The nervous system is divided into two parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
- The CNS is composed of the brain and the spinal cord.
- The PNS consists of all other nerves, sending information to and from the CNS to the rest of the body.
The Peripheral Nervous System (PNS)
- The PNS carries sensory information from the body to the CNS.
- The PNS also sends motor signals from the CNS to different areas of the body, including muscles and glands.
- The PNS has two divisions:
- The Somatic Nervous System: Controls voluntary movements.
- The Autonomic Nervous System: Controls involuntary functions, including heart rate, digestion, and breathing.
- The Autonomic nervous system further splits into:
- The Sympathetic Nervous System: Responsible for "fight or flight" responses, preparing the body for intense activity, increasing heart rate and blood pressure.
- The Parasympathetic Nervous System: Responsible for "rest and digest" functions, calming the body down and conserving energy.
Cells of the Nervous System
- Nervous tissue is made up of three types of cells: neurons, Schwann cells and neuroglial cells.
- Neurons are highly specialized cells that conduct nerve impulses.
- Bundles of neurons are called nerves.
- Neurons have branched processes called dendrites that are receptive in function.
- Neurons have an axon which conducts electrical impulses away from the neuron's cell body.
- Axons can be very long, over 1 meter in some cases!
- Myelin sheaths surround axons in the peripheral nervous system, acting as insulators and promoting rapid transmission of nerve impulses.
Key Features of Neurons
- Cell Body: Contains the nucleus and other important organelles.
- Axon: Responsible for conducting nerve impulses away from the cell body.
- Schwann Cells: Form the myelin sheath around axons in the peripheral nervous system.
- Nodes of Ranvier: Gaps in the myelin sheath that allow for rapid transmission of action potentials.
- Dendrites: Extensions of the cell body that receive information from other neurons.
- Synaptic end bulb: Contains neurotransmitters that are released into the synaptic cleft.
Properties of Neurons
- Irritability: The ability to initiate nerve impulses in response to stimuli.
- Conductivity: The ability to transmit a nerve impulse.
Neuroglial (Glial) Cells
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Neuroglial cells support and protect neurons.
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They are non-excitable cells that continue to replicate throughout life.
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There are three types: Microglia, Astrocytes, and Oligodendrocytes.
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Microglia: Found mainly in the area of blood vessels and act as phagocytes in areas of inflammation and cell destruction.
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Astrocytes: Form the main supporting tissue of the CNS, star shaped with fine branching processes. They lie in a mucopolysaccharide ground substance, found in large numbers adjacent to blood vessels.
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Oligodendrocytes: Smaller than astrocytes, found in clusters around the neurone cell wall and adjacent to myelinated nerve fibers in the CNS. They play a role in forming and maintaining myelin.
The Blood Brain Barrier
- The blood brain barrier is a selective barrier that protects the brain from potentially toxic substances and chemical variations in the blood.
- Allows important nutrients like glucose, water, and oxygen to pass through, but restricts the passing of many drugs, ions, and larger molecules.
Synaptic Transmission
- The synapse is the junction between two neurons where nerve impulses are transmitted.
- The synaptic cleft is the gap between the two neurons.
- The presynaptic neuron releases neurotransmitters into the synaptic cleft.
- Neurotransmitters bind to receptors on the postsynaptic neuron, triggering a nerve impulse in the postsynaptic neuron.
Neurotransmitters
- Neurotransmitters are chemicals that transmit nerve impulses across synapses.
- Over 50 neurotransmitters have been identified.
- Examples include: dopamine, histamine, serotonin, noradrenaline, and acetylcholine.
Local Anesthetics
- Local anesthetics work by reversibly blocking nerve transmission.
- They achieve this by binding to and inhibiting the function of sodium channels in the cell membrane of nerve cells, which prevents the movement of nerve impulses.
Herpes Simplex Virus
- The Herpes Simplex Virus (HSV) can lie dormant in the trigeminal ganglion.
- When reactivated, it travels down the trigeminal nerve, emerging on the lip and causing a cold sore.
Central Nervous System (CNS)
- The central nervous system (CNS) is composed of the brain and the spinal cord.
Brain
- Weighs around 1.4 kg.
- Lies within the cranial cavity.
- Consists of: Cerebrum, Thalamus, Hypothalamus, Midbrain, Pons, Medulla Oblongata, and Cerebellum.
Cerebrum
- Largest part of the brain, responsible for key functions:
- Mental Activities: Memory, intelligence, problem solving, thinking, learning.
- Sensory Perception: Processing of pain, temperature, and touch.
- Initiation and control of voluntary muscle contraction.
- The cerebral cortex is highly wrinkled, increasing the surface area of the brain and the number of neurons.
- The cerebrum is divided into two hemispheres, the left and the right, which are connected by the corpus callosum, a bundle of axons.
Thalamus
- A relay station for sensory and motor signals between the body and the cerebral cortex.
- Receives input from special sense organs (sight, hearing, taste, smell).
Hypothalamus
- Located within the cerebrum, attached to the pituitary gland.
- Controls the release of hormones.
- Controls the autonomic nervous system (involuntary functions like heart rate, digestion, and breathing).
- Involved in emotional reactions, hunger, thirst, body temperature, and biological clocks.
Midbrain
- Connects the cerebrum with the lower parts of the brain and spinal cord.
- Contains nuclei that act as relay stations for nerve fibers.
- Plays a role in auditory and visual reflexes.
Pons
- Bridge between the two hemispheres of the cerebrum.
- Contains nerve fibers that connect the two hemispheres.
- Processes information from several cranial nerves.
Medulla Oblongata
- Continuous with the spinal cord.
- Controls vital functions:
- Cardiovascular center: controls heart rate and blood pressure.
- Respiratory center: controls breathing.
- Reflex centers: coughing, vomiting, sneezing, swallowing.
Cerebellum
- Coordinates voluntary muscle movements.
- Maintains posture and balance.
- Produces smooth movements.
- Receives proprioceptor impulses: Sensory receptors that provide information about body position and movement.
Spinal Cord
- Elongated, almost cylindrical part of the CNS.
- Nerves conveying impulses from the brain to organs and tissues pass through the spinal cord.
- Starts in the medulla oblongata and descends through the spinal column.
Cerebrospinal Fluid (CSF)
- Location: Found in the vertebral canal, surrounded by meninges and cerebrospinal fluid
- Appearance: Clear and colorless
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Function:
- Protection: Acts as a “cushion” or buffer for the brain
- Buoyancy: Reduces the weight of the brain from 1400g to 50g
- Excretion of waste: Transports potentially harmful metabolites, drugs, and other substances away from the brain
- Endocrine medium: Transports hormones to specific areas of the brain
- Renewal rate: Renewed 4-7 times daily
- Components: Contains proteins, glucose, and lymphocytes
Peripheral Nervous System (PNS)
- Function: Network of nerves that connect the central nervous system (CNS) to the body
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Types:
- Somatic nervous system: Voluntary movements
- Autonomic nervous system: Involuntary actions
Autonomic Nervous System
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Branches:
- Sympathetic nervous system: Activates the “fight or flight” response
- Parasympathetic nervous system: Restores the body to a state of calm, the “rest and digest” phase
Spinal Nerves
- Number: 31 pairs
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Breakdown:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
Intervertebral Foramina
- Location: Between vertebrae
- Function: Allow spinal nerves to exit the spinal cord
Cranial Nerves
- Number: 12 pairs
- Function: Primarily control various functions in the head and neck, including sensory input
Peripheral Nerves (location and functions)
- Nerves: Responsible for the communication between the CNS and the rest of the body
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Functions:
- Sensory input (temperature, pain, touch)
- Motor output (muscle movement, gland secretion)
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Description
This quiz focuses on the anatomy and functions of the central nervous system, specifically the brain. It covers key components such as the cerebrum, thalamus, and their respective roles in mental activities and sensory perception. Test your knowledge on how these parts contribute to overall brain function.
