Chapter 44 Flashcards
Sensory organs detect changes and send information to the brain. This happens in two steps:
Transduction – Converts an external stimulus into an internal electrical signal (action potential).
Transmission – Sends the signal to the central nervous system (CNS) for processing.
The human ear
an outer ear,
middle ear, and inner ear
The outer ear
ear funnels pressure waves
into the ear canal
* Where they strike the tympanic
membrane, or eardrum
Hearing: the mammalian ear
The stapes vibrates against the oval window, creating waves in the cochlea’s fluid. Hair cells in the cochlea detect these waves and send signals to the brain for hearing.
lateral line system
- Fish and aquatic amphibians can detect pressure changes in
water
insect compound eye is made of
light-sensing ommatidia
In the vertebrate eye:
Light enters through the pupil and the cornea.
It then passes through the lens, which focuses it onto the retina at the back of the eye.
The retina is attached to the eye by pigmented cells and has three layers:
Photoreceptors (sensitive to light)
Bipolar cells (connect the photoreceptors to ganglion cells)
Ganglion cells (form the innermost layer, their axons carry signals to the brain via the optic nerve).
thermoreception
Animals detect heat energy
electroreception
locate prey, detect
predators, and navigate
* Sensing electric fields
Magnetoreception
Sensing magnetic fields
sarcomere is made up of
two types of proteins:
- Thin filaments
- Thick filaments
actin
Thin filaments are composed
of chains of the protein
myosin
Thick filaments are composed
of multiple strands
In muscle contraction
Actin filaments have troponin and tropomyosin proteins that block the myosin binding sites on actin.
When these binding sites are blocked, myosin can’t interact with actin, causing the muscle to relax.
When calcium ions bind to troponin, it changes the shape of troponin and moves tropomyosin, exposing the myosin binding sites on actin.
This allows myosin and actin to interact, starting muscle contraction.
- Voluntary vs. involuntary muscles:
Voluntary muscles contract when you consciously decide to move them and are controlled by neurons in the somatic division of the nervous system.
Involuntary muscles contract without conscious control and are controlled by neurons in the autonomic division, responding to unconscious electrical signals.
