HSPT504 Lesson 10.1: Nervous System & Sensory Perception

Autonomic Nervous System

  • Organs containing cardiac muscle, smooth muscle, or glands:
    • Airways of the lungs: Smooth muscle
    • Bladder: Smooth muscle
    • Blood vessels: Smooth muscle
    • Digestive tract: Smooth muscle
    • Heart: Cardiac muscle
    • Iris of eye: Smooth muscle
    • Pancreas: Glands
    • Salivary glands: Glands
    • Sweat glands: Glands
    • Uterus: Smooth muscle
  • Autonomic nervous system: Involuntary (no conscious control).
  • States activating sympathetic and parasympathetic divisions:
    • Sympathetic: Fear, fight, stress, running away (fleeing).
    • Parasympathetic: Digesting, relaxation, resting.

Neurotransmitters and Hormones

  • Sympathetic division releases adrenaline and noradrenaline.

Effects of Sympathetic and Parasympathetic Divisions

  • Sympathetic:
    • Airways dilate
    • Bladder relaxes
    • Heart rate and force of contraction increases
    • Decreased blood flow to reproductive system
    • Decreased digestion
    • Glucose released from liver into blood
    • Pupils dilate
  • Parasympathetic:
    • Airways constrict
    • Bladder contracts
    • Heart rate and force of contraction decreases
    • Increased blood flow to reproductive system
    • Increased digestion
    • Pupils constrict
  • Sympathetic and parasympathetic divisions usually have opposite effects on effector organs.

Sensory Perception

  • Processes:
    • Sensation: Reception, transduction.
    • Perception: Interpretation.
  • Senses detect different types of energy.
  • Sense organs and stimuli:
    • Retina of eyes: Lightwaves
    • Olfactory receptors in nasal cavity: Odour molecules
    • Cochlea in ear: Sound waves
  • Transduction: Conversion of different forms of energy into action potentials.
  • Sensory neurons transmit action potentials from receptors to the brain.

Brain and Sensory Information

  • Most incoming sensory information is sent to the thalamus.
  • Olfactory information does not pass through the thalamus.
  • Sensory cortices locations:
    • Vision: Occipital lobe
    • Hearing: Temporal lobe
    • Smell: Frontal lobe
    • Touch: Parietal lobe
  • Sensation is the brain's ability to detect changes in the internal and external environment.

Proprioceptors

  • Types:
    • Muscle spindles: detect muscle length.
    • Golgi tendon organs: detect tension of a muscle.

Receptor Types and Stimuli

  • Chemoreceptors:
    • Stimulus: Changes in chemicals (pH, ion concentration, metabolites e.g. glucose).
  • Thermoreceptors:
    • Stimulus: Temperature changes (warm, cold).
  • Mechanoreceptors:
    • Stimulus: Physical distortion (touch, pressure, vibration).
  • Photoreceptors:
    • Stimulus: Light (photons).
  • Nociceptors:
    • Stimulus: Pain (includes extremes in other types of stimuli) (chemo, thermo, mechano).

Taste

  • Bumps on the surface of the tongue are called taste papillae.
  • Taste buds are located on the walls of the taste papillae.
  • Taste receptors are located on microvilli projecting from the ends of taste cells.
  • When a taste molecule binds with a taste receptor, the taste cell is depolarised.
  • Cranial nerves that transmit action potentials from taste buds to the brain: VII Facial nerve, XI Glossopharyngeal nerve, X Vagus nerve.
  • Taste pathway order:
    • Taste receptor to medulla oblongata
    • Medulla oblongata to thalamus
    • Thalamus to gustatory cortex
  • The gustatory cortex is located in the insula.
  • Five primary taste sensations: Sweet, salty, bitter, sour, savory.
  • Olfaction makes a large contribution to your perception of taste.

Olfactory

  • The olfactory epithelium is located in the superior nasal cavity.
  • Olfactory receptors are located on cilia extending of the dendrites of olfactory receptor cells.
  • Olfactory process
    • Binding of odorant molecules occurs on the cilia of olfactory receptor cells causes them to become depolarised.
    • This binding creates an action potential that is sent to the olfactory bulb.
    • The axons of olfactory receptor cells form the olfactory nerve - the first cranial nerve.
    • The olfactory tract transmits action potentials to the olfactory cortex where most olfactory processing occurs.
  • The olfactory cortex is located in the temporal lobe.
  • Olfactory information does not pass through the thalamus.

Eye

  • 70% of your body's sensory receptors are found in your eyes.

Accessory Structures of the Eye

  • Eyebrow: Shade the eyes from sunlight, prevent sweat from running into the eyes
  • Eyelashes: Touch causes reflex blinking
  • Eyelids: Blink to prevent substances from entering the eye.
  • Conjunctiva: Covers the sclera and inside of eyelids, produces a clear mucus that prevents the eye from drying out
  • Lacrimal gland: Prevents the eyes from drying out
  • Fat pad: Cushions the eye inside the bony orbit

Lacrimal Apparatus

  • Components:
    • Lacrimal gland
    • Ducts of lacrimal gland
    • Lacrimal punctum
    • Lacrimal canaliculus
    • Lacrimal sac
    • Nasolacrimal duct
    • Nostril

Lacrimal Secretions:

  • Components and functions:
    • Moistens the eye surface
    • Clean the eye surface
    • Protect the eye surface from bacterial infection
    • Protect the eye from infection and allergens
    • Antibodies: Protect the eye from infection and allergens
    • Lysosyme: Protect the eye surface from bacterial infection
    • Mucus: Moistens the eye surface, Clean the eye surface
  • Extrinsic eye muscles are formed by skeletal muscle

Internal Eye Structures

  • Choroid
  • Ciliary body
  • Cornea
  • Fovea centralis
  • Iris
  • Lens
  • Optic disc
  • Optic nerve
  • Pupil
  • Retina
  • Sclera
  • Vitreous humor

Fibrous Layer of the Eye

  • Formed by:
    • Sclera: Tough white layer
    • Cornea: Transparent window that allows light to enter the eye
  • Avascular: Contains no blood vessels.

Eye

  • Vascular: That it contains many blood vessels.
  • Blood vessels in the choroid provide nutrition for all layers of the eyeball wall
  • Intraoccular pressure: The pressure of fluid inside the eye

Iris

  • Pupil
  • Circularly arranged smooth muscle fibres
  • Radially arranged smooth muscle fibres

Pupil

  • Circularly arranged smooth muscle fibres innervated by parasympathetic neurons. When these muscle fibres contract:
    • Pupil constricts becomes narrower/smaller
    • Decreases the amount of light entering the eye
  • Radially arranged smooth muscle fibres innervated by sympathetic neurons. When these muscle fibres contract
    • Pupil dilates becomes wider/larger.
    • Increases the amount of light entering the eye

Eye

  • Choroid
  • Optic disc
  • Optic nerve
  • Retina
  • Sclera

Photoreceptors

  • Function: Convert light into action potentials
  • Rods:
    • Respond to low light
    • Provide night time and peripheral vision
  • Cones:
    • Respond to bright light
    • Provide colour vision
  • Rods are more numerous than cones.

Posterior Wall of the Left Eye

  • Optic disc
  • Macula lutea
  • Retinal blood vessels

Vision Information Pathway

  • Visual signals are transported through the optic nerve, first to the thalamus before being directed to the visual cortex.

Visual Pathway

  • Cornea: refracts light
  • Pupil: modulates amount of incoming light
  • Lens: focuses light
  • Retina: transduces light into electrical signals
  • Fovea centralis: area of detailed vision
  • Macula lutea: region surrounding fovea
  • Photoreceptors: rods and cones
  • Optic nerve: transmits visual information to the
  • Thalamus: relays visual information to the
  • Occipital lobe: processes visual information
  • The shape of the lens is controlled by the ciliary muscles.
  • Ciliary muscle relaxed: Lens stretched for distant vision
  • Ciliary muscle contracted: Lens bulging for close vision

Accommodation

  • Muscles that control the shape of the lens are longitudinally arranged.
  • Accommodation for Vision:
    • Close vision:
      • Ciliary muscles contract
      • Lens bulges
      • Light rays are refracted more
    • Distant vision:
      • Ciliary muscles relax
      • Lens flattens
      • Light rays are refracted less
  • The image formed on the retina is upside down compared to the object being viewed.
  • Rectus Muscles of the Left Eye:
    • Medial rectus
    • Lateral rectus
    • Superior rectus
    • Inferior rectus

Visual Pathway

  • From Left and Right Eyes:
    • Optic nerve
    • Optic chiasma
    • Optic tract
    • Thalamus
    • Optic radiation
    • Primary visual cortex

Sound Waves

  • Components:
    • Air molecules are compressed
    • Air molecules are spread out
    • Amplitude of a sound wave
  • Soundwave comparison:
    • Compared to the red soundwave, the blue sound wave has: a higher frequency and greater amplitude
    • Compared to the red soundwave, the green soundwave has: a higher frequency but the amplitude is the same

Ear

  • External ear region (red), the middle ear (green) and the inner ear (blue).

Ear Structure

  • Auricle (pinna)
  • Cochlea
  • Cochlear nerve
  • External auditory canal
  • Ossicles:
  • Semicircular canals
  • Tympanic membrane
  • Vestibular nerve
  • Pharyngotympanic tube

Middle and Inner Ear

  • Malleus
  • Incus
  • Stapes
  • Tympanic membrane
  • Oval window
  • Round window
  • Semicircular canals
  • Vestibule
  • Cochlea
  • Pharyngotympanic tube

Components of the Ear

  • External ear:
    • Auricle
    • External auditory canal
    • Funnels sound waves toward the tympanic membrane
  • Middle ear:
    • Amplifies sound waves ans transmits them to the inner ear
    • Ossicles
    • Pharyngotympanic tube
    • Tympanic membrane
  • Inner ear:
    • Cochlea
    • Semicircular canals
    • Turns vibrations into action potentials
    • Vestibule
  • The function of the pharyngotympanic tube is equalise the air pressure on either side of the tympanic membrane.

Sound Waves

  • A sound wave is a type of pressure wave.
  • Louder sounds have a higher amplitude.
  • Higher pitch sounds have a higher frequency.

Cochlea Structur

  • Organ of Corti
  • Cochlear nerve
  • Tectorial membrane
  • Basilar membrane

Organ of Corti

  • Tectorial membrane
  • Basilar membrane
  • Hair cells
  • Cochlear nerve
  • The Basilar membrane moves in response to waves in the perilymph inside the cochlea.

Hearing

  • Sequence Structure Hearing processes:
    • 1 External auditory canal Outer ear funnels sounds through the external auditory canal to the tympanic membrane.
    • 2 Ossicles Vibrations of the tympanic membrane are transferred by ossicles to the oval window.
    • 3 Cochlear duct Vibrations of the oval window pushes on perilymph liquid in the cochlear duct.
    • 4 Basilar membrane Fluid movements cause the basilar membrane to move up and down bending hair cell cilia.
    • 5 Cilia Bending of cilia depolarises hair cells and creates action potentials
    • 6 Vestibulocochlear nerve Action potentials are transmitted through a vestibulocochlear nerve to the thalamus.
    • 7 Primary auditory cortex The thalamus transmits action potentials to the primary auditory cortex in the temporal lobe of the brain, and you hear.
  • Louder sounds cause more hair cells to move and generate more action potentials.
  • Higher frequency sounds stimulate hair cells that are closer to the oval window.

Vestibular System

  • Two functions:
    • Maintains balance
    • Provides awareness of the body's spatial orientation
  • Components and Movements:
    • Semicircular canals: Rotational movements, Turning of the head
    • Otolithic organs = Saccule and utricle: Head positions, Straight line motions
  • Endolymph fluid is located within the semicircular canals.

Semicircular Canals

  • The enlargements are the ends of the semicircular canals are called ampullae.
  • Each contains hair cells embedded in a gel-like structure called a cupula.
  • When the head turns, endolymph within the canals in the same plane lags behind and briefly moves in the opposite direction.
  • This bends the cupula and the cilia (hairs) embedded in it, depolarising the hair cells and creating action potentials that are sent to the brain.

Saccule and Utricle

  • Saccule:
    • Vertical
    • Bends when a person is lying down
    • Stimulated when you move up or down in an elevator (lift).
  • Utricle:
    • Horizontal
    • Bends when a person is standing upright
    • Stimulated when a car accelerates or decelerates
  • Cilia of the saccule and utricle are embedded in a gel that contains tiny crystals known as otoconia, ear rocks or otoliths.
    • These crystals are formed by Calcium carbonate
    • These crystals add weight to the gel, pulling it down with gravity

Ageing and Senses

  • Cataracts: Cloudiness of the lens, leads to scattering of light and difficulty with night vision
  • Dry eyes: The function of lacrimal glands decreases with age.
  • Impaired balance: From the age of 40, the hair cells in the vestibular system start to degenerate affecting the body's ability to sense and respond to movement and gravity.
  • Macular degeneration: Degeneration of the macula lutea leading to loss of central vision.
  • Presbycusis: Degeneration of hair cells in the Organ of Corti leads first to difficulty hearing high-pitched sounds and difficulty discriminating conversation against background noise. Hair cells are not replaced in the way that smell and taste receptors are.
  • Presbyopia: Decreasing elasticity of the lens reduces its ability to be compressed, leading to difficulty focusing on nearby objects or text.
  • The age-related eye condition in the diagram is Cataracts.