Chapter 16 Flashcards

Receptive Fields

• Definition: The area innervated by a single sensory neuron.

• Not every point on the skin has a nerve; nerves innervate an area.

• Touch is the easiest sense to understand receptive fields.

• Areas with fine touch, like fingertips, have many nerve endings.

• Fingertips:

  • Small receptive fields.

  • High density of nerve endings.

  • Allows for precise touch.

• Elbows:

  • Large receptive fields.

  • Low density of nerve endings.

  • Less precise touch.

• Touching your arm:

  • You can sense the touch but have difficulty pinpointing the exact location.

  • Larger receptive fields mean less accuracy.

• Mosquito bites:

  • Itchiness over a larger area indicates a larger receptive field being stimulated.

Sensitivity and Energy Cost

• Some areas need to be more sensitive than others to sense danger (heat, etc.).

• Why not have everywhere sensitive?

  • Sensory overload.

  • Brain can't filter too many signals at once.

  • Higher energy cost.

• More nerves require more energy for function and processing.

• Small receptive fields:

  • More precision.

  • Increased energy cost.

• The body balances energy expenditure and sensitivity.

  • Numerous small receptive fields where needed (fingertips).

  • Large receptive fields where high sensitivity isn't necessary.

Adaptation

• Definition: Reduced sensitivity to a continually applied stimulus.

• Examples:

  • Not constantly feeling clothes or jewelry.

  • Forgetting you are wearing glasses.

• Nerves get tired and ignore continuous stimuli.

• Nerves reset themselves to be ready for new stimuli.

• Pain adaptation:

  • Tooth pain may disappear, but it doesn't mean it's healed.

  • Nerves get used to the pain and stop sending signals.

  • If tooth pain goes away, see a dentist.

• Pain management:

  • Nurses control pain medication due to adaptation.

  • Explore other care options before increasing pain meds.

General vs. Special Senses

• General Senses: Somatic and visceral receptors.

  • Tactile (touch).

  • Proprioceptors (joint position).

  • Chemical receptors.

  • Thermoreceptors.

• Somatic: Consciously controlled.

• Visceral: Organs.

• Tactile: Touch.

• Proprioceptors: Body's ability to sense its position in space.

  • Not equilibrium (balance).

  • Limb position (e.g., knowing if your hand is up or down without looking).

Proprioceptors

• Detect body and limb movements, skeletal muscle contraction, stretch, and joint pressure.

• Even without movement, you can contract muscles; proprioceptors detect this.

Receptor Types (Slide 8)

• Exteroreceptors: External environment..

• Interoreceptors: Internal organs (visceral).

• Proprioceptors: Limb position in space.

Five Receptor Types

• Chemoreceptors.

• Thermoreceptors.

• Photoreceptors.

• Mechanoreceptors.

• Nociceptors.

Thermoreceptors

• Respond to changes in temperature.

• Detect hot and cold.

Nociceptors

• Respond to pain (external and internal stimuli).

• Specific nerve endings for pain detection.

• Some people lack functional nociceptors and must be careful to avoid injuries.

Mechanoreceptors

• Detect changes in pressure, stretch, or distension.

• Three types:

  • Baroreceptors.

  • Proprioceptors.

  • Tactile receptors.

Baroreceptors

• Detect changes in pressure caused by stretch or distension.

• Found in the heart (detect blood pressure) and lungs (detect breathing).

Photoreceptors

• Detect changes in color, intensity, and movement of light.

• Located in the retina of the eyes.

Referred Pain (Slide 21)

• Definition: Pain felt in a location different from its source.

• Example: Heart attack pain felt in the left arm.

• Due to cutaneous and visceral sensory neurons conducting signals on the same ascending tracts in the spinal cord.

• The brain incorrectly localizes the pain stimulus.

• Nerve tracks (lateral corticospinal, medial lemniscus) decussate (cross over) in the medulla oblongata or brainstem.

Olfactory Pathway

• Some odors cause visceral reactions (gagging).

• Olfactory nerve (cranial nerve I) is for smell.

• Olfactory tract projects directly to the primary olfactory cortex, hypothalamus, amygdala, and other regions.

• Gagging in response to bad smells is due to the hypothalamus.

• The olfactory pathway shares a tract with the pharynx, protecting the body from ingested toxins.

Eye Anatomy (Slides 43, 55, 56, 63)

• Eyebrows prevent sweat from dripping into the eyes and aid in communication.

• Anterior chamber: Contains aqueous humor (watery).

• Posterior chamber: Contains vitreous humor (gelatinous).

• Iris functions as a diaphragm, controlling the pupil size (hole into the eyeball).

• Layers of the eye (from outside in):

  • Sclera: White of the eye.

  • Choroid: Contains veins and arteries.

  • Retina: Innermost layer with rods and cones.

• Optic nerve (cranial nerve II) creates a blind spot in the retina.

• Fovea centralis: Area of the retina with the most rods and cones for clear, straight-ahead vision.

Visual Impairments

• Astigmatism: The eye loses its round shape, causing skewed images.

• Presbyopia: (Senior eyes/old age eyes) Lenses lose roundness due to slackening ligaments, making it hard to see close-up.

• Eye exercises can strengthen eye muscles to improve eyesight, especially for age-related vision issues.

Rods and Cones

• Photoreceptors in the retina, named for their shapes under a microscope.

• Rods: Sensitive to light but only see in black and white; function in dim light.

• Cones: See color and detail; concentrated at the fovea centralis.

• Pigmented layer of the retina requires vitamin A for photoreceptor cell function.

• Vitamin A deficiency can worsen eyesight.

• Carrots contain vitamin A and can improve eyesight if you are deficient.

Optic Chiasm

• The location where the optic nerves from each eye cross over to the opposite side of the brain.

• Axons from the medial region of each retina cross to the opposite side of the brain.

• Lateral sides of the nerves stay on the same side.

• This crossover is essential for stereoscopic vision (depth perception).

Stereoscopic Vision (Depth Perception)

• Two eyes provide two images that the brain combines for depth perception.

• One eye can perceive some depth but not as well as two eyes.

Ear Structure and Function (Slide 113)

• Ear contains bones (malleus) that vibrate the eardrum for hearing.

• The ear is also responsible for equilibrium (balance) via fluid-filled tubes.

• Fluid and hairs in the tubes detect movement and orientation.

• Problems with balance can be related to hearing issues (tinnitus).

Pitch vs. Loudness

• Frequency: Measured in hertz (Hz), determines pitch (high or low note).

  • Thinner guitar string vibrates faster (higher note).

• Loudness: Measured in decibels (dB), determined by wave amplitude.

• Decibel scale is logarithmic (scale of tens); small changes in decibels represent large increases in sound intensity.