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Questions and Answers
What is the main role of the cerebellum?
What is the main role of the cerebellum?
The thalamus is responsible for regulating sleep cycles.
The thalamus is responsible for regulating sleep cycles.
False
What type of fibers connect the two hemispheres of the brain?
What type of fibers connect the two hemispheres of the brain?
Commissural fibers
The _____ is referred to as the olfactory brain.
The _____ is referred to as the olfactory brain.
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Match the following brain structures with their primary functions:
Match the following brain structures with their primary functions:
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Which part of the brain processes visual information in birds?
Which part of the brain processes visual information in birds?
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White matter is located above the cortical layer of the brain.
White matter is located above the cortical layer of the brain.
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Which of the following structures is NOT part of the central nervous system?
Which of the following structures is NOT part of the central nervous system?
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What is the principal regulator of the autonomic nervous system?
What is the principal regulator of the autonomic nervous system?
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The pia mater is the thick, outermost layer of the meninges.
The pia mater is the thick, outermost layer of the meninges.
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What is the primary role of cerebrospinal fluid?
What is the primary role of cerebrospinal fluid?
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The _______ is responsible for the conscious experience of sensory input.
The _______ is responsible for the conscious experience of sensory input.
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What does the central nervous system primarily do?
What does the central nervous system primarily do?
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Match the following components of the CNS with their descriptions:
Match the following components of the CNS with their descriptions:
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The blood-brain barrier allows all substances to easily pass into the brain.
The blood-brain barrier allows all substances to easily pass into the brain.
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Name the three layers of the meninges.
Name the three layers of the meninges.
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What is the primary function of the midbrain?
What is the primary function of the midbrain?
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The olfactory and optic nerves are the only purely sensory cranial nerves that exit the brain stem.
The olfactory and optic nerves are the only purely sensory cranial nerves that exit the brain stem.
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Name the cranial nerve that is most widely distributed throughout the body.
Name the cranial nerve that is most widely distributed throughout the body.
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The spinal cord consists of five regions: cervical, thoracic, lumbar, sacral, and ______.
The spinal cord consists of five regions: cervical, thoracic, lumbar, sacral, and ______.
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Match the following cranial nerves with their primary function:
Match the following cranial nerves with their primary function:
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Which part of the brain controls respiratory movements?
Which part of the brain controls respiratory movements?
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What type of matter in the spinal cord contains myelinated fibers?
What type of matter in the spinal cord contains myelinated fibers?
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The dorsal horn of the spinal cord is responsible for motor functions.
The dorsal horn of the spinal cord is responsible for motor functions.
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Study Notes
Organization of the CNS
- The CNS is comprised of the brain and spinal cord.
- The brain consists of the cerebrum (forebrain), diencephalon (thalamus and hypothalamus), cerebellum, mesencephalon, pons, and medulla oblongata (brain stem).
Task of the CNS
- The CNS receives continuous information from both inside and outside the body.
- It analyzes and interprets this information to make sense of the internal and external environment.
- The CNS sends commands to the body to:
- Maintain function of vital systems and organs
- Respond to the external environment
Meninges and Cerebrospinal Fluid
- The meninges are three layers surrounding the brain and spinal cord:
- Dura mater: the outermost, thick, and tough layer
- Arachnoid: the middle layer
- Pia mater: the innermost layer, tightly attached to the neural tissue
- Cerebrospinal fluid (CSF) circulates within the CNS, located in the subarachnoid space between the arachnoid and pia mater.
- CSF:
- Is formed by capillaries in the pia mater called choroid plexus.
- Circulates from the brain's ventricles down to the central canal of the spinal cord.
- Diffuses from the fourth ventricle into the subarachnoid space and circulates around the brain and spinal cord.
- Drains into venous sinus before entering blood circulation.
- Plays several roles:
- Provides nutrients to the CNS.
- Acts as a shock absorber, providing protection.
- Maintains ionic concentration ideal for optimal neuronal function.
- Facilitates blood-CSF barrier at the choroid plexus, regulating uptake of nutrients and drugs into the CSF.
Blood Brain Barrier
- The blood-brain barrier restricts the passage of cells, proteins, and most amino acids.
- Only liposoluble substances, such as gases, can easily diffuse through this barrier.
Cerebrum
- The cerebral cortex, the outer layer, is responsible for conscious experience of sensory input and high nervous association.
- It is highly educable and has mapped primary cortical areas (mainly in humans).
- The cerebral cortex is divided into areas based on anatomical structure and response to stimulation.
- Anatomically defined areas:
- Sensory (somesthetic) cortex
- Motor cortex
- Areas without defined reactions are considered association cortex.
- Anatomically defined areas:
- White matter located beneath the cortex comprises myelinated nerve fibers that include:
- Association fibers: connecting different parts of the cortex
- Commissural fibers: connecting the two hemispheres
- Projection fibers: connecting the cortex to other brain structures and the spinal cord
- Basal nuclei:
- Located deep within the cerebrum, near the thalamus.
- Paired nuclei composed of large neuron pools.
- Control complex semi-voluntary movements, such as walking and running.
- Work in conjunction with the cortex and cerebellum.
- In birds, they also control voluntary movements.
Cerebellum
- The cerebellum is crucial for coordination and smooth movement, but not involved in consciousness or sensation.
- It:
- Receives information from the inner ear (equilibrium), proprioceptive receptors (muscles, tendons, and joints), and the cortex (visual and motor).
- Prevents distortion of intended movement.
- Receives information about body status and intended movement.
- Makes adjustments for smooth movement completion.
- Sends corrective signals via the thalamus to the cortex and spinal nuclei responsible for muscle control.
- Is well developed in animals requiring precise movement adjustments in various environments (air, ground, water).
Diencephalon
- The diencephalon, also known as the interbrain, includes the hypothalamus, thalamus, and epithalamus.
- The thalamus serves as a relay station for sensory information, the cerebellum and basal ganglia, and the cerebral cortex.
- The epithalamus contains the olfactory correlation center and the pineal gland.
- The hypothalamus:
- Produces neuropeptides that control the anterior pituitary.
- Produces neurohormones released by the posterior pituitary.
- Plays a significant role in regulating the autonomic nervous system, alongside the brainstem, making it a central component of homeostasis control.
Brain Stem
- It contains nuclei responsible for governing body functions through reflexes.
- It also consists of a large amount of white matter involved in conveying information.
Mesencephalon (Midbrain)
- It comprises the visual reflex center:
- Receives visual information.
- Controls eye movement for focus.
- It contains the auditory reflex center which triggers the head turning response to noise.
- In birds, the mesencephalon is well developed for processing visual information.
- In most mammals, the midbrain is small and covered by the cortex.
Pons and Medulla Oblongata
- Together they contain centers for postural reflexes (hopping, righting, placing) and control respiratory movements.
- The medulla oblongata is crucial for:
- Controlling heart activity.
- Regulating blood pressure.
- Managing the relative distribution of blood to organs.
Cranial Nerves
- There are 12 pairs of cranial nerves.
- The olfactory (I) and optic (II) nerves are purely sensory and remain within the brain.
- Nerves III-XII exit from the brain stem and innervate structures in the head and neck; most are mixed, carrying both sensory and motor information.
- The Vagus nerve (X) is an exception, being the most widely distributed nerve in the body, extending from the neck to the abdomen.
- It carries parasympathetic fibers to visceral structures in the thorax and abdomen.
Spinal Cord
- It has cervical, thoracic, lumbar, sacral, and coccygeal regions, with the number of segments varying between species.
- The spinal cord is comprised of white matter and grey matter.
- White matter:
- Contains myelinated (giving the white appearance) and unmyelinated nerve fibers (axons).
- Arranged in columns or "tracts".
- Grey matter:
- Contains cell bodies and dendrites.
- Shaped like a butterfly with three zones:
- Dorsal horn: sensory
- Ventral horn: motor (skeletal muscles) and autonomic fibers
- Middle zone: association
- White matter:
Spinal Nerves
- Spinal nerves are formed by the joining of dorsal and ventral roots within the spinal canal.
- They emerge from intervertebral foramina and are numbered according to the corresponding vertebra.
- Each spinal segment receives sensory information from a section of the skin (dermatomes) and sends information to muscles (myotomes). This information helps predict the effects of spinal cord injury.
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Description
Explore the intricate organization of the Central Nervous System (CNS), including its key components such as the brain and spinal cord. Learn about the tasks performed by the CNS, like information processing and bodily responses, as well as the protective layers and cerebrospinal fluid essential for its functionality.
