Nervous System Anatomy A

Nervous System Anatomy A

Objectives

• Learn the terms used to describe the anatomy of the nervous system, including:

  • The distinction between the central and peripheral nervous systems.

  • Anatomical directions in the nervous system.

• Gain an understanding of:

  • The structure of the spinal cord.

  • The structure and function of the autonomic nervous system.

  • Major components of the central nervous system.

Introduction

• Our nervous systems directly control all of our behavior.

• The lecture emphasizes a 'my' nervous system perspective, encouraging personal engagement with the material.

Human Nervous System: Structure and Function

• Central Nervous System (CNS):

  • Components: Brain and spinal cord.

  • Function: Integrative and control centers.

• Peripheral Nervous System (PNS):

  • Components: Cranial nerves and spinal nerves.

  • Function: Communication lines between the CNS and the rest of the body.

• Sensory (Afferent) Division:

  • Components: Somatic and visceral sensory nerve fibers.

  • Function: Conducts impulses from receptors to the CNS.

• Motor (Efferent) Division:

  • Components: Motor nerve fibers.

  • Function: Conducts impulses from the CNS to effectors (muscles and glands).

    • Autonomic Nervous System (ANS):

      • Function: Visceral motor (involuntary); conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands.

      • Divisions:

        • Sympathetic Division: Mobilizes body systems during activity ("fight or flight").

        • Parasympathetic Division: Conserves energy and promotes "housekeeping" functions during rest.

    • Somatic Nervous System:

      • Function: Somatic motor (voluntary); conducts impulses from the CNS to skeletal muscles.

Peripheral Nervous System (PNS) Details

• Autonomic NS:

  • Sends and receives messages to regulate autonomic behaviors (e.g., heart rate, respiration, digestion).

• Somatic NS:

  • Controls voluntary muscles.

  • Conveys sensory information to the CNS.

Autonomic Nervous System (ANS) Details

• Parasympathetic NS:

  • Facilitates vegetative, non-emergency responses.

  • Conserves bodily resources.

  • Postganglionic axons mostly release acetylcholine.

• Sympathetic NS:

  • Network of nerves preparing organs for rigorous activity.

  • Mobilizes bodily resources.

  • Mostly uses norepinephrine.

Spinal Cord

• Part of the CNS within the spinal column.

• Extends from the base of the brain to just below the waist, with a segmented structure.

• Communicates with sense organs and muscles (except those of the head).

• Sensory Nerves: Bring sensory information from the body to the brain (entering dorsal roots).

• Motor Nerves: Transmit motor information from the brain to the body (exiting ventral roots).

• Consists of two types of matter:

  • Grey matter:

    • Located in the center of the spinal cord.

    • Densely packed with cell bodies and dendrites.

  • White matter:

    • Composed mostly of myelinated axons.

    • Carries information from the grey matter to the brain or other areas of the spinal cord.

• Spinal Reflexes: Occur independently of the brain.

  • Interneurons in the spinal cord receive sensory input and excite motor neurons, controlling muscles that withdraw the limb.

Major Components of the Central Nervous System (CNS)

• Spinal Cord

• Brain

  • Hindbrain

    • Medulla

    • Pons

    • Cerebellum

  • Midbrain

    • Tectum

    • Tegmentum

  • Forebrain

    • Thalamus

    • Hypothalamus

    • Limbic System

    • Cerebral Cortex

Anatomical Directions

Brainstem

• Comprised of:

  • Hindbrain structures.

  • Midbrain structures.

  • Thalamus.

Hindbrain

• Located at the posterior portion of the brain.

• Consists of the:

  • Medulla

  • Pons

  • Cerebellum

Medulla

• Located just above the spinal cord.

• Comprised of ascending and descending tracts.

• Small nuclei at its core form the reticular formation.

• Responsible for vital reflexes such as breathing, heart rate, vomiting, salivation, coughing, and sneezing.

• Damage is often fatal.

Cranial Nerves

• Twelve pairs of nerves that enter and exit the brain directly.

• Allow the medulla to control:

  • Sensations from the head.

  • Muscle movements in the head.

  • Many parasympathetic outputs.

Cranial Nerves: Names and Major Functions

Pons

• Fiber tract that lies on each side of the medulla (ventral and anterior).

• The term "pons" is Latin for "bridge."

• Axons from each half of the brain cross to the opposite side of the spinal cord (contralateral control).

Cerebellum

• Also known as the "little brain."

• Structure with many deep folds.

• Helps regulate motor movement, balance, and coordination.

• Important for shifting attention between auditory and visual stimuli.

• Greatly affected by alcohol.

Midbrain

• Contains the following structures:

  • Tectum:

    • Roof of the midbrain.

    • Composed of superior and inferior colliculi (process sensory information).

  • Tegmentum:

    • Nuclei for cranial nerves and part of the reticular formation.

    • Red nucleus and substantia nigra (both involved in sensorimotor function).

    • Periaqueductal gray

Forebrain

• The most anterior and prominent part of the mammalian brain, with two cerebral hemispheres.

• Consists of the outer cortex and subcortical regions.

• The outer portion is known as the "cerebral cortex."

• Each side receives sensory information and controls motor movement from the opposite (contralateral) side of the body.

Forebrain: Subcortical Regions

• Structures underneath the cortex.

• Hypothalamus and thalamus form the diencephalon.

Hypothalamus

• Small area near the base, just below the thalamus (hypo = below).

• Conveys messages to the pituitary gland to alter hormone release.

• Associated with motivated behaviors (e.g., eating, drinking, sexual behavior).

Thalamus

• Large two-lobed structure at the top of the brain stem.

• Relay station from the sensory organs (except smell); main source of input to the cortex.

• Integrates information across senses.

Information Routes from Thalamus to Cerebral Cortex

• Lateral geniculate nuclei: vision

• Medial geniculate nuclei: hearing

• Ventral posterior nuclei: touch

Pituitary Gland

• Hormone-producing gland found at the base of the hypothalamus.

Basal Ganglia

• Comprises the caudate nucleus, putamen, and the globus pallidus.

• Associated with planning of motor movement and aspects of memory and emotional expression.

• Critical for gradual learning of skills and habits.

Basal Forebrain

• Composed of several structures that lie on the dorsal surface of the forebrain.

• Contains the nucleus basalis.

  • Receives input from the hypothalamus and basal ganglia.

  • Sends axons that release acetylcholine to the cerebral cortex.

  • Important in arousal, wakefulness, and attention.

Limbic System

• Consists of interlinked structures forming a border around the brainstem.

• Includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex.

Limbic System Function

• Associated with motivated and emotional behavior (e.g., eating, drinking, sexual activity, anxiety, and aggression).

Hippocampus

• Large structure located between the thalamus and cerebral cortex (toward the posterior portion of the forebrain).

• Critical for certain types of memory, especially memories for individual events.

Ventricles

• Four fluid-filled cavities within the brain’s central canal containing cerebrospinal fluid (CSF).

• Two lateral ventricles + 3rd ventricle and 4th ventricle.

• CSF provides cushioning for the brain.

• CSF is a reservoir of hormones and nutrition for the CNS.

Meninges

• Membranes that surround the brain and spinal cord.

  • Dura mater

  • Arachnoid mater

  • Pia mater

• Contain pain receptors.

• Cerebrospinal fluid flows through the spaces between the brain and meninges.

Objectives

• Learn the terms used to describe the anatomy of the nervous system, including:

  • The distinction between the central and peripheral nervous systems. Understand how these systems interact and their specific roles in the body.

  • Anatomical directions in the nervous system. Learn to navigate and describe locations within the nervous system using precise directional terminology.

• Gain an understanding of:

  • The structure of the spinal cord. Explore its organization, including the arrangement of gray and white matter, and its function as a communication pathway.

  • The structure and function of the autonomic nervous system. Investigate the roles of its sympathetic and parasympathetic divisions in maintaining homeostasis.

  • Major components of the central nervous system. Identify and describe the key structures of the brain and their functions.

Introduction

• Our nervous systems directly control all of our behavior. Understand how neural activity translates into actions and responses.

• The lecture emphasizes a 'my' nervous system perspective, encouraging personal engagement with the material. Consider how the nervous system functions in your own body.

Human Nervous System: Structure and Function

• Central Nervous System (CNS):

  • Components: Brain and spinal cord. The brain processes information, while the spinal cord relays signals.

  • Function: Integrative and control centers. The CNS interprets sensory input and coordinates responses.

• Peripheral Nervous System (PNS):

  • Components: Cranial nerves and spinal nerves. These nerves extend from the brain and spinal cord to the rest of the body.

  • Function: Communication lines between the CNS and the rest of the body. The PNS carries sensory information to the CNS and motor commands from the CNS.

• Sensory (Afferent) Division:

  • Components: Somatic and visceral sensory nerve fibers. These fibers detect stimuli from the body's surface and internal organs.

  • Function: Conducts impulses from receptors to the CNS. Sensory information is transmitted to the brain for processing.

• Motor (Efferent) Division:

  • Components: Motor nerve fibers. These fibers carry signals from the CNS to muscles and glands.

  • Function: Conducts impulses from the CNS to effectors (muscles and glands).

  • Autonomic Nervous System (ANS):

    • Function: Visceral motor (involuntary); conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands. The ANS regulates essential functions like heart rate and digestion.

    • Divisions:

    • Sympathetic Division: Mobilizes body systems during activity ("fight or flight"). Prepares the body for action in response to stress or danger; increases heart rate, dilates pupils, etc.

    • Parasympathetic Division: Conserves energy and promotes "housekeeping" functions during rest. Promotes relaxation and conserves energy by slowing heart rate, stimulating digestion, etc.

  • Somatic Nervous System:

    • Function: Somatic motor (voluntary); conducts impulses from the CNS to skeletal muscles. Controls voluntary movements like walking and talking.

Peripheral Nervous System (PNS) Details

• Autonomic NS:

  • Sends and receives messages to regulate autonomic behaviors (e.g., heart rate, respiration, digestion). Maintains homeostasis by controlling involuntary functions.

• Somatic NS:

  • Controls voluntary muscles. Enables conscious control of movement.

  • Conveys sensory information to the CNS. Provides feedback about the body's interaction with the environment.

Autonomic Nervous System (ANS) Details

• Parasympathetic NS:

  • Facilitates vegetative, non-emergency responses. Promotes relaxation and energy conservation.

  • Conserves bodily resources. Supports long-term survival.

  • Postganglionic axons mostly release acetylcholine. Acetylcholine is the primary neurotransmitter in the parasympathetic nervous system.

• Sympathetic NS:

  • Network of nerves preparing organs for rigorous activity. Prepares the body for intense physical activity.

  • Mobilizes bodily resources. Increases alertness, heart rate, and respiration.

  • Mostly uses norepinephrine. Norepinephrine is a key neurotransmitter in the sympathetic nervous system.

Spinal Cord

• Part of the CNS within the spinal column. Connects the brain to the rest of the body.

• Extends from the base of the brain to just below the waist, with a segmented structure. Protected by the vertebral column.

• Communicates with sense organs and muscles (except those of the head). Relays sensory and motor information between the brain and body.

• Sensory Nerves: Bring sensory information from the body to the brain (entering dorsal roots). Dorsal roots are specialized for sensory input.

• Motor Nerves: Transmit motor information from the brain to the body (exiting ventral roots). Ventral roots are specialized for motor output.

• Consists of two types of matter:

  • Grey matter:

  • Located in the center of the spinal cord. Contains neuronal cell bodies and synapses.

  • Densely packed with cell bodies and dendrites. Site of information processing.

  • White matter:

  • Composed mostly of myelinated axons. Facilitates rapid communication.

  • Carries information from the grey matter to the brain or other areas of the spinal cord. Forms ascending and descending tracts.

• Spinal Reflexes: Occur independently of the brain. Enable rapid responses to stimuli.

  • Interneurons in the spinal cord receive sensory input and excite motor neurons, controlling muscles that withdraw the limb. Provides a protective mechanism.

Major Components of the Central Nervous System (CNS)

• Spinal Cord

• Brain

  • Hindbrain

  • Medulla: Controls vital functions.

  • Pons: Relays information and regulates states of arousal.

  • Cerebellum: Coordinates movement and balance.

  • Midbrain

  • Tectum: Processes sensory information.

  • Tegmentum: Involved in motor control and reward.

  • Forebrain

  • Thalamus: Relays sensory and motor signals to the cerebral cortex, and regulates consciousness, sleep, and alertness.

  • Hypothalamus: Regulates fundamental functions like hunger, thirst and body temperature.

  • Limbic System: Involved in emotions, memory, and motivation.

  • Cerebral Cortex: Responsible for higher-level cognitive functions, such as decision making and planning.

Anatomical Directions

Brainstem

• Comprised of:

  • Hindbrain structures. Medulla, pons, and cerebellum.

  • Midbrain structures. Tectum and tegmentum.

  • Thalamus. Relays sensory information.

Hindbrain

• Located at the posterior portion of the brain. Connects the brain to the spinal cord.

• Consists of the:

  • Medulla. Controls vital functions.

  • Pons. Relays information and regulates arousal.

  • Cerebellum. Coordinates movement and balance.

Medulla

• Located just above the spinal cord. Continuous with the spinal cord.

• Comprised of ascending and descending tracts. Facilitates communication between the brain and body.

• Small nuclei at its core form the reticular formation. Regulates arousal and attention.

• Responsible for vital reflexes such as breathing, heart rate, vomiting, salivation, coughing, and sneezing. Essential for survival.

• Damage is often fatal. Can result in loss of vital functions.

Cranial Nerves

• Twelve pairs of nerves that enter and exit the brain directly. Provide sensory and motor innervation to the head and neck.

• Allow the medulla to control:

  • Sensations from the head. Touch, temperature, and pain.

  • Muscle movements in the head. Facial expressions and chewing.

  • Many parasympathetic outputs. Regulation of heart rate and digestion.

Cranial Nerves: Names and Major Functions

Pons

• Fiber tract that lies on each side of the medulla (ventral and anterior). Acts as a bridge connecting different parts of the brain.

• The term "pons" is Latin for "bridge." Facilitates communication.

• Axons from each half of the brain cross to the opposite side of the spinal cord (contralateral control). Ensures that each side of the brain controls the opposite side of the body.

Cerebellum

• Also known as the "little brain." Important for motor control and coordination.

• Structure with many deep folds. Increases surface area for neural processing.

• Helps regulate motor movement, balance, and coordination. Essential for smooth, accurate movements.

• Important for shifting attention between auditory and visual stimuli. Contributes to cognitive functions.

• Greatly affected by alcohol. Leads to impaired motor control and balance.

Midbrain

• Contains the following structures:

  • Tectum:

  • Roof of the midbrain. Located dorsally.

  • Composed of superior and inferior colliculi (process sensory information). Involved in auditory and visual reflexes.

  • Tegmentum:

  • Nuclei for cranial nerves and part of the reticular formation. Regulates arousal and motor control.

  • Red nucleus and substantia nigra (both involved in sensorimotor function). Contribute to movement coordination.

  • Periaqueductal gray: involved in pain modulation, particularly in response to fear stimuli

Forebrain

• The most anterior and prominent part of the mammalian brain, with two cerebral hemispheres. Responsible for higher-level cognitive functions.

• Consists of the outer cortex and subcortical regions. Includes the cerebral cortex, thalamus, hypothalamus, and limbic system.

• The outer portion is known as the "cerebral cortex." Site of conscious thought, perception, and voluntary movement.

• Each side receives sensory information and controls motor movement from the opposite (contralateral) side of the body. Ensures that each hemisphere controls the opposite side of the body.

Forebrain: Subcortical Regions

• Structures underneath the cortex. Include the thalamus, hypothalamus, basal ganglia, and limbic system.

• Hypothalamus and thalamus form the diencephalon. Important for regulating homeostasis and relaying sensory information.

Hypothalamus

• Small area near the base, just below the thalamus (hypo = below). Regulates essential functions.

• Conveys messages to the pituitary gland to alter hormone release. Influences endocrine function.

• Associated with motivated behaviors (e.g., eating, drinking, sexual behavior). Plays a role in survival and reproduction.

Thalamus

• Large two-lobed structure at the top of the brain stem. Relays sensory and motor information.

• Relay station from the sensory organs (except smell); main source of input to the cortex. Filters and prioritizes sensory information.

• Integrates information across senses. Contributes to perception and awareness.

Information Routes from Thalamus to Cerebral Cortex

• Lateral geniculate nuclei: vision

• Medial geniculate nuclei: hearing

• Ventral posterior nuclei: touch

Pituitary Gland

• Hormone-producing gland found at the base of the hypothalamus. Regulates growth, metabolism, and reproduction.

Basal Ganglia

• Comprises the caudate nucleus, putamen, and the globus pallidus. Involved in motor control and learning.

• Associated with planning of motor movement and aspects of memory and emotional expression. Contributes to habit formation and emotional regulation.

• Critical for gradual learning of skills and habits. Enables the acquisition of new motor skills.

Basal Forebrain

• Composed of several structures that lie on the dorsal surface of the forebrain. Includes the nucleus basalis and other nuclei.

• Contains the nucleus basalis.

  • Receives input from the hypothalamus and basal ganglia. Integrates information from different brain regions.

  • Sends axons that release acetylcholine to the cerebral cortex. Modulates cortical activity.

  • Important in arousal, wakefulness, and attention. Contributes to cognitive functions.

Limbic System

• Consists of interlinked structures forming a border around the brainstem. Involved in emotions, memory, and motivation.

• Includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex. Each structure contributes to specific aspects of emotion and memory.

Limbic System Function

• Associated with motivated and emotional behavior (e.g., eating, drinking, sexual activity, anxiety, and aggression). Plays a role in survival and reproduction.

Hippocampus

• Large structure located between the thalamus and cerebral cortex (toward the posterior portion of the forebrain). Essential for memory formation.

• Critical for certain types of memory, especially memories for individual events. Enables the encoding of new episodic memories.

Ventricles

• Four fluid-filled cavities within the brain’s central canal containing cerebrospinal fluid (CSF). Protect and nourish the brain.

• Two lateral ventricles + 3rd ventricle and 4th ventricle. Interconnected chambers.

• CSF provides cushioning for the brain. Protects against injury.

• CSF is a reservoir of hormones and nutrition for the CNS. Supplies essential nutrients.

Meninges

• Membranes that surround the brain and spinal cord.

  • Dura mater: tough, outer layer

  • Arachnoid mater: weblike, middle layer

  • Pia mater: delicate, inner layer

• Contain pain receptors. Sensitive to pressure and inflammation.

• Cerebrospinal fluid flows through the spaces between the brain and meninges. Provides cushioning and support.

Objectives

• Learn the terms used to describe the anatomy of the nervous system, including:

  • The distinction between the central and peripheral nervous systems. Understand how these systems interact and their specific roles in the body.

  • Anatomical directions in the nervous system. Learn to navigate and describe locations within the nervous system using precise directional terminology.

• Gain an understanding of:

  • The structure of the spinal cord. Explore its organization, including the arrangement of gray and white matter, and its function as a communication pathway.

  • The structure and function of the autonomic nervous system. Investigate the roles of its sympathetic and parasympathetic divisions in maintaining homeostasis.

  • Major components of the central nervous system. Identify and describe the key structures of the brain and their functions.

Introduction

• Our nervous systems directly control all of our behavior. Understand how neural activity translates into actions and responses.

• The lecture emphasizes a 'my' nervous system perspective, encouraging personal engagement with the material. Consider how the nervous system functions in your own body.

Human Nervous System: Structure and Function

• Central Nervous System (CNS):

  • Components: Brain and spinal cord. The brain processes information, while the spinal cord relays signals.

  • Function: Integrative and control centers. The CNS interprets sensory input and coordinates responses.

• Peripheral Nervous System (PNS):

  • Components: Cranial nerves and spinal nerves. These nerves extend from the brain and spinal cord to the rest of the body.

  • Function: Communication lines between the CNS and the rest of the body. The PNS carries sensory information to the CNS and motor commands from the CNS.

• Sensory (Afferent) Division:

  • Components: Somatic and visceral sensory nerve fibers. These fibers detect stimuli from the body's surface and internal organs.

  • Function: Conducts impulses from receptors to the CNS. Sensory information is transmitted to the brain for processing.

• Motor (Efferent) Division:

  • Components: Motor nerve fibers. These fibers carry signals from the CNS to muscles and glands.

  • Function: Conducts impulses from the CNS to effectors (muscles and glands).

  • Autonomic Nervous System (ANS):

    • Function: Visceral motor (involuntary); conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands. The ANS regulates essential functions like heart rate and digestion.

    • Divisions:

    • Sympathetic Division: Mobilizes body systems during activity ("fight or flight"). Prepares the body for action in response to stress or danger; increases heart rate, dilates pupils, etc.

    • Parasympathetic Division: Conserves energy and promotes "housekeeping" functions during rest. Promotes relaxation and conserves energy by slowing heart rate, stimulating digestion, etc.

  • Somatic Nervous System:

    • Function: Somatic motor (voluntary); conducts impulses from the CNS to skeletal muscles. Controls voluntary movements like walking and talking.

Peripheral Nervous System (PNS) Details

• Autonomic NS:

  • Sends and receives messages to regulate autonomic behaviors (e.g., heart rate, respiration, digestion). Maintains homeostasis by controlling involuntary functions.

• Somatic NS:

  • Controls voluntary muscles. Enables conscious control of movement.

  • Conveys sensory information to the CNS. Provides feedback about the body's interaction with the environment.

Autonomic Nervous System (ANS) Details

• Parasympathetic NS:

  • Facilitates vegetative, non-emergency responses. Promotes relaxation and energy conservation.

  • Conserves bodily resources. Supports long-term survival.

  • Postganglionic axons mostly release acetylcholine. Acetylcholine is the primary neurotransmitter in the parasympathetic nervous system.

• Sympathetic NS:

  • Network of nerves preparing organs for rigorous activity. Prepares the body for intense physical activity.

  • Mobilizes bodily resources. Increases alertness, heart rate, and respiration.

  • Mostly uses norepinephrine. Norepinephrine is a key neurotransmitter in the sympathetic nervous system.

Spinal Cord

• Part of the CNS within the spinal column. Connects the brain to the rest of the body.

• Extends from the base of the brain to just below the waist, with a segmented structure. Protected by the vertebral column.

• Communicates with sense organs and muscles (except those of the head). Relays sensory and motor information between the brain and body.

• Sensory Nerves: Bring sensory information from the body to the brain (entering dorsal roots). Dorsal roots are specialized for sensory input.

• Motor Nerves: Transmit motor information from the brain to the body (exiting ventral roots). Ventral roots are specialized for motor output.

• Consists of two types of matter:

  • Grey matter:

  • Located in the center of the spinal cord. Contains neuronal cell bodies and synapses.

  • Densely packed with cell bodies and dendrites. Site of information processing.

  • White matter:

  • Composed mostly of myelinated axons. Facilitates rapid communication.

  • Carries information from the grey matter to the brain or other areas of the spinal cord. Forms ascending and descending tracts.

• Spinal Reflexes: Occur independently of the brain. Enable rapid responses to stimuli.

  • Interneurons in the spinal cord receive sensory input and excite motor neurons, controlling muscles that withdraw the limb. Provides a protective mechanism.

Major Components of the Central Nervous System (CNS)

• Spinal Cord

• Brain

  • Hindbrain

  • Medulla: Controls vital functions.

  • Pons: Relays information and regulates states of arousal.

  • Cerebellum: Coordinates movement and balance.

  • Midbrain

  • Tectum: Processes sensory information.

  • Tegmentum: Involved in motor control and reward.

  • Forebrain

  • Thalamus: Relays sensory and motor signals to the cerebral cortex, and regulates consciousness, sleep, and alertness.

  • Hypothalamus: Regulates fundamental functions like hunger, thirst and body temperature.

  • Limbic System: Involved in emotions, memory, and motivation.

  • Cerebral Cortex: Responsible for higher-level cognitive functions, such as decision making and planning.

Anatomical Directions

Brainstem

• Comprised of:

  • Hindbrain structures. Medulla, pons, and cerebellum.

  • Midbrain structures. Tectum and tegmentum.

  • Thalamus. Relays sensory information.

Hindbrain

• Located at the posterior portion of the brain. Connects the brain to the spinal cord.

• Consists of the:

  • Medulla. Controls vital functions.

  • Pons. Relays information and regulates arousal.

  • Cerebellum. Coordinates movement and balance.

Medulla

• Located just above the spinal cord. Continuous with the spinal cord.

• Comprised of ascending and descending tracts. Facilitates communication between the brain and body.

• Small nuclei at its core form the reticular formation. Regulates arousal and attention.

• Responsible for vital reflexes such as breathing, heart rate, vomiting, salivation, coughing, and sneezing. Essential for survival.

• Damage is often fatal. Can result in loss of vital functions.

Cranial Nerves

• Twelve pairs of nerves that enter and exit the brain directly. Provide sensory and motor innervation to the head and neck.

• Allow the medulla to control:

  • Sensations from the head. Touch, temperature, and pain.

  • Muscle movements in the head. Facial expressions and chewing.

  • Many parasympathetic outputs. Regulation of heart rate and digestion.

Cranial Nerves: Names and Major Functions

Pons

• Fiber tract that lies on each side of the medulla (ventral and anterior). Acts as a bridge connecting different parts of the brain.

• The term "pons" is Latin for "bridge." Facilitates communication.

• Axons from each half of the brain cross to the opposite side of the spinal cord (contralateral control). Ensures that each side of the brain controls the opposite side of the body.

Cerebellum

• Also known as the "little brain." Important for motor control and coordination.

• Structure with many deep folds. Increases surface area for neural processing.

• Helps regulate motor movement, balance, and coordination. Essential for smooth, accurate movements.

• Important for shifting attention between auditory and visual stimuli. Contributes to cognitive functions.

• Greatly affected by alcohol. Leads to impaired motor control and balance.

Midbrain

• Contains the following structures:

  • Tectum:

  • Roof of the midbrain. Located dorsally.

  • Composed of superior and inferior colliculi (process sensory information). Involved in auditory and visual reflexes.

  • Tegmentum:

  • Nuclei for cranial nerves and part of the reticular formation. Regulates arousal and motor control.

  • Red nucleus and substantia nigra (both involved in sensorimotor function). Contribute to movement coordination.

  • Periaqueductal gray: involved in pain modulation, particularly in response to fear stimuli

Forebrain

• The most anterior and prominent part of the mammalian brain, with two cerebral hemispheres. Responsible for higher-level cognitive functions.

• Consists of the outer cortex and subcortical regions. Includes the cerebral cortex, thalamus, hypothalamus, and limbic system.

• The outer portion is known as the "cerebral cortex." Site of conscious thought, perception, and voluntary movement.

• Each side receives sensory information and controls motor movement from the opposite (contralateral) side of the body. Ensures that each hemisphere controls the opposite side of the body.

Forebrain: Subcortical Regions

• Structures underneath the cortex. Include the thalamus, hypothalamus, basal ganglia, and limbic system.

• Hypothalamus and thalamus form the diencephalon. Important for regulating homeostasis and relaying sensory information.

Hypothalamus

• Small area near the base, just below the thalamus (hypo = below). Regulates essential functions.

• Conveys messages to the pituitary gland to alter hormone release. Influences endocrine function.

• Associated with motivated behaviors (e.g., eating, drinking, sexual behavior). Plays a role in survival and reproduction.

Thalamus

• Large two-lobed structure at the top of the brain stem. Relays sensory and motor information.

• Relay station from the sensory organs (except smell); main source of input to the cortex. Filters and prioritizes sensory information.

• Integrates information across senses. Contributes to perception and awareness.

Information Routes from Thalamus to Cerebral Cortex

• Lateral geniculate nuclei: vision

• Medial geniculate nuclei: hearing

• Ventral posterior nuclei: touch

Pituitary Gland

• Hormone-producing gland found at the base of the hypothalamus. Regulates growth, metabolism, and reproduction.

Basal Ganglia

• Comprises the caudate nucleus, putamen, and the globus pallidus. Involved in motor control and learning.

• Associated with planning of motor movement and aspects of memory and emotional expression. Contributes to habit formation and emotional regulation.

• Critical for gradual learning of skills and habits. Enables the acquisition of new motor skills.

Basal Forebrain

• Composed of several structures that lie on the dorsal surface of the forebrain. Includes the nucleus basalis and other nuclei.

• Contains the nucleus basalis.

  • Receives input from the hypothalamus and basal ganglia. Integrates information from different brain regions.

  • Sends axons that release acetylcholine to the cerebral cortex. Modulates cortical activity.

  • Important in arousal, wakefulness, and attention. Contributes to cognitive functions.

Limbic System

• Consists of interlinked structures forming a border around the brainstem. Involved in emotions, memory, and motivation.

• Includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex. Each structure contributes to specific aspects of emotion and memory.

Limbic System Function

• Associated with motivated and emotional behavior (e.g., eating, drinking, sexual activity, anxiety, and aggression). Plays a role in survival and reproduction.

Hippocampus

• Large structure located between the thalamus and cerebral cortex (toward the posterior portion of the forebrain). Essential for memory formation.

• Critical for certain types of memory, especially memories for individual events. Enables the encoding of new episodic memories.

Ventricles

• Four fluid-filled cavities within the brain’s central canal containing cerebrospinal fluid (CSF). Protect and nourish the brain.

• Two lateral ventricles + 3rd ventricle and 4th ventricle. Interconnected chambers.

• CSF provides cushioning for the brain. Protects against injury.

• CSF is a reservoir of hormones and nutrition for the CNS. Supplies essential nutrients.

Meninges

• Membranes that surround the brain and spinal cord.

  • Dura mater: tough, outer layer

  • Arachnoid mater: weblike, middle layer

  • Pia mater: delicate, inner layer

• Contain pain receptors. Sensitive to pressure and inflammation.

• Cerebrospinal fluid flows through the spaces between the brain and meninges. Provides cushioning and support.