ANPH 1001 Unit 3 Topic 2 Special senses Viola Manokore

ANPH 1001 Unit 3: Special Senses

• Instructor: Viola Manokore

• Institution: Norquest Colleges

References

• Rizzo, D.C. (2016). Fundamentals of anatomy and physiology (4th ed.). Cengage Learning

• Institution: Norquest Colleges

Chapter 11: The Nervous System

• Focus Areas:

  • The Brain

  • Cranial Nerves

  • Autonomic Nervous System

  • Special Senses

Introduction to Brain Structures

1. Brainstem

• Function: Controls breathing, heartbeat rates, and reactions to auditory and visual stimuli.

• Components:

  • Medulla oblongata

  • Pons varolii

  • Midbrain

2. Diencephalon

• Function: Controls homeostasis.

• Components:

  • Thalamus

  • Hypothalamus

3. Cerebrum

• Function: Governs intellectual processes and emotions.

4. Cerebellum

• Function: Maintains posture and balance.

Autonomic Nervous System

• Controls all involuntary functions of the body.

• Special senses include sight, hearing, balance, smell, and taste.

Principal Parts of the Brain

• Average Weight: About 3 pounds in adults.

• Protection:

  • Cranial bones

  • Meninges (similar structure to spinal meninges)

  • Cerebrospinal fluid (circulates through subarachnoid space)

Ventricles

• Description: Cavities within the brain that connect with each other, the subarachnoid space, and the central canal of the spinal cord.

• Function: Cerebrospinal fluid serves as shock absorbers for the CNS and circulates nutrients.

Anatomy & Functions of the Brainstem

Components of Brainstem

• Medulla oblongata

• Pons varolii

• Midbrain

• Function: Connects the brain to the spinal cord.

• Importance: Delicate structure; damage to small parts may lead to death.

Functions of Medulla Oblongata

• Ascending & descending tracts connect spinal cord with the brain.

• Reticular formation controls consciousness and arousal.

Reflex Centers of Medulla Oblongata

• Vasomotor: Regulates blood vessels' diameter.

• Cardiac: Regulates heartbeat.

• Medullary rhythmicity: Controls breathing rhythm.

Pons Varolii

• Acts as a bridge between the spinal cord and brain.

• Helps control breathing through pneumotaxic and apneustic areas.

Midbrain

• Mesencephalon: Conveys impulses from the cerebral cortex to pons and spinal cord.

• Dorsal Tectum: Reflex center for eye and head movements in response to visual stimuli.

Anatomy & Functions of Diencephalon

• Location: Superior to midbrain and between cerebral hemispheres.

• Main Areas:

  • Thalamus: Interpretation center for pain and temperature.

  • Hypothalamus: Controls homeostasis, ANS, and mind-body interaction (e.g., appetite, emotions).

Cerebrum: Structure & Function

• Main Components:

  • Frontal lobe

  • Parietal lobe

  • Temporal lobe

  • Occipital lobe

Cerebral Cortex

• Composed of gray matter with gyri (folds) and sulci (grooves) to increase surface area.

• Functions: Controls motor functions, interprets sensory impulses, regulates emotions, and intellectual processes.

The Cerebellum: Structure & Function

• Structure: Butterfly-shaped with two partially separated hemispheres connected by vermis.

• Functions:

  • Coordinates muscular movements

  • Maintains posture

  • Maintains balance

The Autonomic Nervous System

• Functions: Operates without conscious effort to regulate internal organ functions and maintain homeostasis.

Divisions of ANS

1. Sympathetic: Prepares the body for stress and energy-demanding situations (e.g., increases heart rate).

2. Parasympathetic: Restores the body to a non-stressful state (e.g., stimulates digestion).

Cranial Nerves and Their Functions

• (I) Olfactory: Smell

• (II) Optic: Sight

• (III) Oculomotor: Eye movement and pupil constriction

• (IV) Trochlear: Eye movement

• (V) Trigeminal: Chewing and sensations in teeth

• (VI) Abducens: Eye movement

• (VII) Facial: Facial expression, taste, tear & salivary glands

• (VIII) Vestibulocochlear: Equilibrium and hearing

• (IX) Glossopharyngeal: Swallowing, taste, salivary glands

• (X) Vagus: Muscle movements, sensory impulses, heart rate regulation

• (XI) Accessory: Swallowing, head movement

• (XII) Hypoglossal: Swallowing, speech

The Sense of Smell

• Mechanism: Molecules in the air dissolve in nasal mucus, activating bipolar sensory neurons which transmit impulses to the olfactory bulbs.

• Brain interpretation of odors varies.

The Sense of Taste

• Structure: Taste buds on the tongue, palate, and pharynx.

• Major Taste Categories: Sweet, sour, salty, and bitter.

• Taste perception affected by olfaction (e.g., holding nose reduces taste).

The Sense of Sight

Eye Protection

• Eyelids, eyelashes, and tears lubricate and protect the eyes.

Anatomy of the Eye

1. Sclera: Outermost layer, tough connective tissue.

2. Choroid: Middle layer with blood vessels and pigment cells.

3. Retina: Innermost layer, contains light-sensitive cells (rods & cones).

4. Iris: Regulates light entry.

5. Macula Lutea: Contains fovea centralis for sharpest vision.

Disorders of the Eye

• Glaucoma: Increased pressure in aqueous humor leading to potential blindness.

The Sense of Hearing & Equilibrium

Outer Ear Components

• Auricle: Flexible part allowing sound waves entry.

• External Auditory Meatus: Lined with hair and ceruminous glands (ear wax production).

Middle Ear Functions

• Tympanic Membrane: Vibrates in response to sound, separating external ear from the middle ear.

• Eustachian Tubes: Equalize pressure for clear hearing.

Aging and the Nervous System

• Changes in head size and neurons during early life.

• Loss of synaptic contacts and neurotransmitters with aging leading to slower responses and increased stroke risk.

Disorders of the Nervous System

• Meningitis: Inflammation of meninges, can lead to severe consequences.

• Cerebral Palsy: Brain damage during development or birth.

• Myopia: Nearsightedness; Hyperopia: Farsightedness; Color blindness: Inability to perceive certain colors.

• Glaucoma: Excessive pressure affecting vision.

Summary of Key Points

• Principal parts of the brain and their functions have been discussed.

• 12 cranial nerves named and their roles examined.

• Role of the autonomic nervous system and its divisions clarified.

• Overview of special senses and their associated structures provided.

ANPH 1001 Unit 3: Special Senses

Instructor: Viola ManokoreInstitution: Norquest Colleges

References

Rizzo, D.C. (2016). Fundamentals of anatomy and physiology (4th ed.). Cengage LearningInstitution: Norquest Colleges

Chapter 11: The Nervous System

Focus Areas:

• The Brain

• Cranial Nerves

• Autonomic Nervous System

• Special Senses

Introduction to Brain Structures

1. Brainstem

   • Function: The brainstem controls involuntary functions such as breathing, heartbeat, and reactions to stimuli like sound and light.

   • Components:

     • Medulla oblongata: regulates autonomic functions vital for survival

     • Pons varolii: relays signals between the cerebellum and the cerebrum

     • Midbrain: plays a key role in vision and hearing

2. Diencephalon

   • Function: The diencephalon plays a crucial role in maintaining homeostasis and relaying sensory information.

   • Components:

     • Thalamus: serves as a relay station for sensory and motor signals

     • Hypothalamus: controls autonomic nervous system functions while regulating emotional responses such as hunger and thirst.

3. Cerebrum

   • Function: The cerebrum is responsible for higher brain functions including thought processes, sensory perception, and emotional regulation.

4. Cerebellum

   • Function: The cerebellum is essential for coordination of voluntary movements, posture, and balance.

Autonomic Nervous System

• Controls: The autonomic nervous system regulates involuntary functions such as heart rate, digestion, and respiratory rate, allowing the body to maintain a stable internal environment despite external changes.

• Special senses include: The senses of sight, hearing, balance, smell, and taste, which allow humans to perceive and interact with their environment.

Principal Parts of the Brain

• Average Weight: Approximately 3 pounds in adults.

• Protection:

  • Cranial bones: shield the brain against physical trauma

  • Meninges: three protective membranes (dura mater,arachnoid mater, pia mater) that encompass the brain

  • Cerebrospinal fluid: circulates in the subarachnoid space, cushioning the brain and providing nutrients

  • Ventricles: These hollow spaces within the brain connect with the central canal of the spinal cord and help circulate cerebrospinal fluid, which provides essential nutrients and removes waste.

Anatomy & Functions of the Brainstem

• Components of Brainstem

  • Medulla oblongata, Pons varolii, and Midbrain

  • Function: Acts as a critical communication pathway between the brain and spinal cord. Damage to the brainstem can result in severe consequences, including loss of basic life functions.

• Functions of Medulla Oblongata:

  • Contains ascending and descending tracts connecting the spinal cord with the brain, facilitating communication.

  • The reticular formation within the medulla controls consciousness, alertness, and sleep-wake cycles.

• Reflex Centers of Medulla Oblongata:

  • Vasomotor: Regulates blood vessel diameter, influencing blood pressure

  • Cardiac: Modulates heartbeat and contractility

  • Medullary rhythmicity: Governs the rhythm and rate of breathing, essential for maintaining life.

• Pons Varolii:

  • Acts as a conduit between the spinal cord and the brain, facilitating the controls of autonomic functions such as breathing via specialized nuclei.

• Midbrain:

  • Also known as mesencephalon; important for relaying impulses between the cerebral cortex, pons, and spinal cord.

  • The dorsal tectum functions as a reflex center for visual and auditory stimuli, influencing head and eye movements.

Anatomy & Functions of Diencephalon

• Location: Positioned superior to the midbrain and between the two cerebral hemispheres, serving as a central hub for sensory and regulatory functions.

• Main Areas:

  • Thalamus: Acts as a relay station for nearly all sensory information before it reaches the cerebral cortex, including pain and temperature sensation, enabling interpretation and response.

  • Hypothalamus: Involved in regulating crucial bodily functions, including thermoregulation, hunger, thirst, and emotional responses, as well as controlling the autonomic nervous system and endocrine system for comprehensive homeostasis.

Cerebrum: Structure & Function

• Main Components:

  • Frontal lobe: Responsible for decision-making, problem-solving, and controlling social behaviors

  • Parietal lobe: Processes sensory information and spatial orientation

  • Temporal lobe: Involved in auditory processing and memory storage

  • Occipital lobe: Primarily responsible for visual processing and interpretation

• Cerebral Cortex: The outer layer of the cerebrum comprised of gray matter, featuring gyri (folds) to increase surface area for enhanced neural connections, aiding in complex thought processes, sensory interpretation, and emotional regulation.

The Cerebellum: Structure & Function

• Structure: A butterfly-shaped structure with two hemispheres linked by a region called the vermis, playing a crucial role in motor control.

• Functions: Date coordinate voluntary movements, ensuring precise motor control, posture stability, and balance during body movements.

The Autonomic Nervous System

• Functions: Regulates internal organs without conscious effort, critical for sustaining life by continuously adjusting bodily functions in reaction to external stimuli.

• Divisions of ANS:

  • Sympathetic: Activates the fight-or-flight response to prepare the body for stressful situations, increasing heart rate and redirecting blood flow to muscles

  • Parasympathetic: Restores the body to a resting state, promoting functions like digestion and energy conservation, effectively counterbalancing the sympathetic response.

Cranial Nerves and Their Functions

• (I) Olfactory: Smell detection

• (II) Optic: Visual perception

• (III) Oculomotor: Controls eye movement and adjusts pupil size

• (IV) Trochlear: Eye movement regulation

• (V) Trigeminal: Facilitates chewing and sensory information from teeth and face

• (VI) Abducens: Governs lateral eye movement

• (VII) Facial: Responsible for facial expression movements, taste sensations, and stimulation of tear and salivary glands

• (VIII) Vestibulocochlear: Involved in hearing and maintaining balance

• (IX) Glossopharyngeal: Supports swallowing, taste sensations, and salivary gland function

• (X) Vagus: Plays a crucial role in heart rate control and various involuntary muscle movements

• (XI) Accessory: Aids in head movement and swallowing

• (XII) Hypoglossal: Controls movements of the tongue essential for speech and swallowing.

The Sense of Smell

• Mechanism: Olfactory sensory receptors in the nasal cavity detect molecules dissolved in mucous, sending signals to the brain for interpretation. The perception of odors is subjective and can vary among individuals.

The Sense of Taste

• Structure: Taste receptors located within taste buds primarily on the tongue, palate, and pharynx interact with food chemicals.

• Major Taste Categories: Sweet, sour, salty, bitter, and umami (savory). Smell significantly influences taste perception; obstructing olfactory senses can diminish taste experience.

The Sense of Sight

• Eye Protection: The eyelids, eyelashes, and tear production act as barriers against dust and harmful substances to the eyes.

• Anatomy of the Eye:

  • Sclera: The tough outer layer providing structural integrity

  • Choroid: Supplies blood to the eye and contains pigments to absorb excess light

  • Retina: The inner layer containing rods and cones that convert light into visual signals

  • Iris: Controls light entry through pupil size adjustments

  • Macula Lutea: The area responsible for sharp central vision, specifically the fovea centralis.

• Disorders of the Eye:

  • Glaucoma: A condition characterized by increased intraocular pressure, potentially leading to blindness if untreated.

The Sense of Hearing & Equilibrium

• Outer Ear Components

  • Auricle: The pinna structures that funnel sound waves into the ear canal

  • External Auditory Meatus: Contains ceruminous glands producing earwax for protective purposes.

• Middle Ear Functions:

  • Tympanic Membrane: Vibrates in response to sound waves, separating the outer ear from the middle ear, essential for sound amplification

  • Eustachian Tubes: Maintain equal pressure in the middle ear, allowing for optimal sound transmission.

Aging and the Nervous System

• Changes in the nervous system include a decrease in head size and a reduction in neuron number with age.

• Aging has been associated with decreased synaptic contacts and neurotransmitter levels, leading to slower reflexes and a heightened risk of strokes.

Disorders of the Nervous System

• Meningitis: An inflammation of the protective membranes encompassing the brain and spinal cord, often resulting from infection, and can have severe consequences.

• Cerebral Palsy: A group of disorders affecting movement and muscle tone caused by brain damage during development or birth.

• Visual Disorders:

  • Myopia: Nearsightedness where close objects are seen clearly but distant ones are blurry.

  • Hyperopia: Farsightedness resulting in difficulty focusing on nearby objects.

  • Color blindness: A genetic condition preventing the ability to distinguish between certain colors.

  • Glaucoma: Elevated ocular pressure that can damage the optic nerve and loss of vision.

Summary of Key Points

• The principal parts of the brain and their various functions have been thoroughly examined.

• All 12 cranial nerves have been identified along with their essential roles.

• The autonomic nervous system and its two main divisions, sympathetic and parasympathetic, have been clarified in relation to maintaining homeostasis.

• A comprehensive overview of special senses and their associated structures has been provided, illustrating their importance in daily life and overall health.