Nervous System Part 2 Flashcards
(17 cards)
What are the two main divisions of the nervous system?
Central Nervous System (CNS): Brain and spinal cord.
Peripheral Nervous System (PNS): All nerves outside the CNS, including cranial and spinal nerves
What is the function of the CNS?
Controls most functions of the body and mind, processing information and coordinating responses.
What are the components and roles of the PNS?
Sensory neurons (afferent): Carry information from receptors to CNS.
Motor neurons (efferent): Carry instructions from CNS to effectors (muscles/glands).
Enables communication between CNS and rest of body.
What protects the brain and spinal cord?
Cerebrospinal fluid (CSF): Shock absorber.
Blood-brain barrier: Separates brain from blood-borne toxins and pathogens
What is the autonomic nervous system?
A branch of the PNS that controls involuntary body functions. It has two divisions:
Sympathetic: Prepares body for “fight or flight” (e.g., increased heart rate).
Parasympathetic: Calms the body (“rest and digest” mode).
What is a reflex and why does it bypass the brain?
A reflex is a rapid, involuntary response to a stimulus. It is processed by the spinal cord to ensure a quicker reaction and avoid damage.
What are receptors and what types are there?
Receptors detect stimuli and send signals via sensory neurons.
Types:
Chemoreceptors: Detect chemicals (e.g., taste, smell)
Thermoreceptors: Detect temperature
Mechanoreceptors: Detect pressure/touch
Photoreceptors: Detect light
How do sensory organs relate to receptors?
Sensory organs contain receptors that convert environmental stimuli into nerve impulses. Examples include:
Eyes (photoreceptors)
Ears (mechanoreceptors)
Nose (chemoreceptors)
Skin (mechanoreceptors & thermoreceptors)
Tongue (chemoreceptors)
What are the main structures of the eye and their functions?
Cornea & Lens: Refract light to focus on retina
Iris & Pupil: Regulate light entry
Retina: Contains photoreceptors (rods and cones)
Optic nerve: Carries impulses to the brain
Aqueous & Vitreous humour: Maintain eye shape
Ciliary body: Adjusts lens shape for focusing
What are rods and cones?
Rods: Function in low light, black-and-white vision, high sensitivity, low detail
Cones: Function in bright light, allow color vision, high detail (visual sharpness)
What pigments do rods and cones contain?
Rods: Rhodopsin (splits into opsin and retinal when light hits)
Cones: Iodopsins, each sensitive to specific colours (e.g., red, green, blue in primates)
What is bleaching in photoreceptors?
The process where rhodopsin in rods splits due to light exposure, leading to depolarization and generation of action potentials.
How do photoreceptor distributions vary between species?
Birds: Cones for violet, blue, green, red – may see UV light for foraging
Dogs: Cones for violet and yellow-green
Nocturnal animals: More rod cells, large eyes, slit pupils, tapetum lucidum
What is the tapetum lucidum?
A reflective layer behind the retina that enhances low-light vision by reflecting light back through the photoreceptors.
What is the pupillary light reflex and its purpose?
An involuntary reflex controlled by the autonomic nervous system that adjusts pupil size based on light levels to protect photoreceptors
Compare prey and predator eye adaptations.
Prey: Eyes on sides of head (monocular vision), wide field, better predator detection
Predators: Forward-facing eyes (binocular vision), depth perception, good for hunting
What is the visual field of prey vs predators?
Prey (e.g. sheep, ducks): ~270° visual field
Predators (e.g. cats, owls): ~110°, focused forward for 3D vision
