1. Conscious and subconscious awareness of changes in the external or internal environment. ...

Conscious and subconscious awareness of changes in the external or internal environment.

Components of sensation: Stimulation of the sensory receptor → transduction of the stimulus → generation of nerve impulses → integration of sensory input.

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General senses: somatic and visceral.Somatic- tactile, thermal, pain and proprioceptive sensations.Visceral- provide information about conditions within internal organs.

Special senses- smell, taste, vision, hearing and equilibrium or balance.

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Free nerve endings: pain and thermoreceptors.

Encapsulated nerve endings: pacinian corpuscles.

Separate cells: hair cells, photoreceptors and gustatory receptor cells.

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Generator potential is produced by free nerve endings, encapsulated nerve endings, and olfactory receptors. When it reaches a threshold, it triggers one or more nerve impulses in the axon of a first-order sensory neuron.

Receptor potential triggers the release of neurotransmitter → postsynaptic potential → action potential.

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Exteroceptors Interoceptors Proprioceptors

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Mechanoreceptors Thermoreceptors Nociceptors Photoreceptors Chemoreceptors Osmoreceptors

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Rapidly adapting receptors: receptors that detect pressure, touch and smell.

Slowly adapting receptors: receptors that detect pain, body position, and chemical composition of the blood.

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Sensory receptors in the skin (cutaneous sensations), muscles, tendons and joints and in the inner ear.

Uneven distribution of receptors. Four modalities: tactile, thermal, pain

and proprioceptive.

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Include touch, pressure, vibration, itch and tickle.

Tactile receptors in the skin are Meissner corpuscles, hair root plexuses, Merkel discs, Ruffini corpuscles, pacinian corpuscles, and free nerve endings.

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Egg-shaped mass of dendrites enclosed by a capsule of connective tissue.

Rapidly adapting receptors. Found in the dermal papillae of hairless

skin such as in the fingertips, hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris, and tip of the penis.

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Rapidly adapting touch receptors found in the hairy skin.

Free nerve endings wrapped around hair follicles.

Detect movements on the skin surface that disturb hairs.

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Also known as type I cutaneous mechanoreceptors.

Slowly adapting touch receptors. Saucer-shaped, flattened free nerve

endings. Found in the fingertips, hands, lips, and

external genitalia.

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Also called as type II cutaneous mechanoreceptors.

Elongated, encapsulated receptors. Located deep in the dermis and in

ligaments and tendons. Found in the hands, and soles.

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Large oval structure composed of a multilayered connective tissue capsule that encloses a dendrite.

Fast adapting receptors. Found around joints, tendons, and

muscles; in the periosteum, mammary glands, external genitalia, pancreas and urinary bladder.

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Thermoreceptors are free nerve endings.

Two distinct thermal sensations: cold receptors- warm receptors-

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Protective. Sensory receptors are nociceptors. Free nerve endings. Two types of pain: fast and slow. Fast pain: acute, sharp or pricking pain. Slow pain: chronic, burning, aching or

throbbing pain.

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Pain is felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimulated organ.

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Receptors are called proprioceptors. Slow adaptation. Weight discrimination. Three types: muscle spindles, tendon

organs and joint kinesthetic receptors.

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Interspersed among most skeletal muscle fibers and aligned parallel to them.

Measure muscle stretching. Consists of intrafusal muscle fibers-

specialized muscle fibers with sensory nerve endings and motor neurons called gamma motor neurons.

Extrafusal muscle fibers- surrounding muscle fibers supplied by alpha motor neurons.

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Located at the junction of a tendon and a muscle.

Protect tendons and their associated muscles from damage due to excessive tension.

Consists of a thin capsule of connective tissue that encloses a few tendon fascicles.

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Found within or around the articular capsules of synovial joints.

Free nerve endings and Ruffini corpuscles in the capsules of joints respond to pressure.

Pacinian corpuscles respond to acceleration and deceleration of joints during movement.

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First-order neuron(somatic receptor to the brain stem/spinal cord)

→ second order neuron(brain stem/spinal cord too the thalamus; decussate)

→ third-order neuron(thalamus to the primary somatosensory area of the cortex).

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The posterior column-medial lemniscus pathway.

The anterolateral (spinothalamic) pathway.

The trigeminothalamic pathway. The anterior and posterior

spinocerebellar pathway.

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Conveys nerve impulses for touch, pressure, vibration and conscious proprioception from the limbs, trunk, neck, and posterior head to the cerebral cortex.

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Conveys nerve impulses for pain, cold, warmth, itch, and tickle from the limbs, trunk, neck, and posterior head to the cerebral cortex.

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Conveys nerve impulses for most somatic sensations from the face, nasal cavity, oral cavity and teeth to the cerebral cortex.

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Mapping of the postcentral gyrus.

Size of the cortical region representing a body part depends on the sensory impulses received from that part.

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Upper motor neurons → lower motor neurons → skeletal muscles.

Neural circuits involving basal ganglia and cerebellum regulate activity of the upper motor neurons.

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Direct motor pathway- originates in the cerebral cortex.Corticospinal pathway: to the limbs and trunk.Corticobulbar pathway: to the head.

Indirect motor pathway- originates in the brain stem.

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Located in the precentral gyrus of the frontal lobe.

More cortical area is devoted to those muscles involved in skilled, complex or delicate movements.

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Originate in the brain stem. Include: Rubrospinal tractTectospinal tractVestibulospinal tractReticulospinal tract

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The cerebellum coordinates and smoothes contractions of skeletal muscles during skilled movements and helps maintain posture and balance.

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Sagittalplane

Motor areas ofcerebral cortex

Thalamus

Correctivefeedback

Motor centers inbrainstem

Pons

Pontine nuclei

Direct pathways

Indirect pathways

Signals to lowermotor neurons

Sagittal section through brain and spinal cord

Sensory signals fromproprioceptors in musclesand joints, vestibularapparatus, and eyes

Cortex ofcerebellum

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Sagittalplane


Correctivefeedback

Pons

Direct pathways

Indirect pathways




Cortex ofcerebellum

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2

Thalamus


Pontine nuclei

Sagittalplane


Correctivefeedback

Pons

Direct pathways

Indirect pathways




Cortex ofcerebellum

1

2

3

Thalamus


Pontine nuclei

Sagittalplane


Correctivefeedback

Pons

Direct pathways

Indirect pathways




Cortex ofcerebellum

1

2

4

3

Thalamus


Pontine nuclei

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Wakefulness and sleep- Learning and memory-

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Consists of neurons whose axons project from the reticular formation through the thalamus to the cerebral cortex.

Increased activity of the RAS causes awakening from sleep (arousal).

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A state of altered consciousness. Two components: non-rapid eye

movement (NREM) sleep and rapid eye movement (REM) sleep.

NREM sleep consists of four stages:Stage 1-Stage 2-Stage 3-Stage 4-

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Learning is the ability to acquire new information or skills through instruction or experience.

Memory is the process by which information acquired through learning is stored and retrieved.

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Immediate memory- recall for a few seconds.

Short-term memory- temporary ability to recall.

Long-term memory- more permanent. Memory consolidation.

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The receptors for olfaction, which are bipolar neurons, are in the nasal epithelium in the superior portion of the nasal cavity.

Substances to be smelled must be volatile, water-soluble, and lipid-soluble.

In olfactory reception, a generator potential develops and triggers one or more nerve impulses.

Adaptation to odors occurs quickly and the threshold of smell is low; only a few molecules of certain substances need be present in air to be smelled.

Olfactory receptors convey nerve impulses to olfactory (I) nerves, olfactory bulb, olfactory tracts, and the cerebral (perpyriform) cortex and the limbic system.

The receptors for gustation, the gustatory receptor cells, are located in taste buds.

Substances to be tasted must be in solution in saliva.

Receptor potentials developed in gustatory hairs cause the release of neurotransmitter which gives rise to nerve impulses.

The five primary tastes are: sour, salty, bitter, sweet and umami (Japanese for “meaty/brothy”).

Adaptation to taste occurs quickly, the threshold varies with the taste involved.

Gustatory receptor cells convey nerve impulses to cranial nerves V, VII, IX and X, the medulla, the thalamus, and the parietal lobe of the cerebral cortex.

The study of the structure, function and diseases of the eye is known as ophthalmology; a physician who specializes in diagnosis and treatment of eye disorders with drugs, surgery, and corrective lenses is known as an ophthalmologist.

An optometrist is a specialist with a degree in optometry who is licensed to examine and test the eyes and treat visual defects by prescribing corrective lenses.

An optician is a technician (not a doctor) who fits, adjusts, and dispenses corrective lenses prescribed by an ophthalmologist or optometrist.

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1. Conscious and subconscious awareness of changes in the external or internal environment. ...

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