Spinal Cord Anatomy and Function

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Questions and Answers

What marks the end of the spinal cord proper?

Thoracic Region

Cauda Equina

Cervical Enlargement

Conus Medullaris (correct)

Where are somatic motor neurons primarily located within the spinal cord?

Lateral horn

Ventral horn (correct)

Dorsal horn

Dorsal root ganglia

Which pathway is responsible for carrying fine touch and proprioception sensations?

Corticospinal Pathway

Spinothalamic Pathway

Dorsal Column-Medial Lemniscal Pathway (correct)

Cerebellar Pathway

A lesion affecting motor neurons in the brain or spinal cord prior to the synapse in the spinal cord is known as which type?

Upper Motor Neuron Lesion Signup and view all the answers

Damage to which area of the spinal cord is likely to cause loss of sensation?

Dorsal Horn Signup and view all the answers

What type of receptors detect internal stimuli, such as stretch in digestive organs?

Interoceptors Signup and view all the answers

Which type of motor neuron directly innervates muscles?

Somatic Motor Neurons Signup and view all the answers

What symptom is associated with Lower Motor Neuron lesions?

Flaccid paralysis Signup and view all the answers

Which type of receptor is specifically responsible for detecting vibrations?

Pacinian Corpuscles Signup and view all the answers

What is the correct sequence of the spinal reflex arc?

Stimulus → Receptor → Sensory Neuron → Integration Center → Motor Neuron → Effector Signup and view all the answers

Which neurotransmitter is primarily associated with the sympathetic nervous system?

Norepinephrine Signup and view all the answers

Which type of stimuli do nociceptors primarily respond to?

Pain from mechanical, thermal, or chemical sources Signup and view all the answers

What is the role of the thalamus in perceptual processing?

To serve as a relay station for sensory information Signup and view all the answers

Which action is associated with the activation of the parasympathetic nervous system?

Promoting digestion Signup and view all the answers

What is the function of the semicircular canals in the ear?

To detect rotational movement of the head Signup and view all the answers

What type of receptor responds to chemicals in food for taste detection?

Gustatory receptors Signup and view all the answers

Which part of the retina is responsible for sharp central vision?

Fovea Centralis Signup and view all the answers

Which statement correctly describes the sympathetic nervous system?

It prepares the body for 'fight or flight' responses Signup and view all the answers

Study Notes

Spinal Cord (CNS)

Conus Medullaris: Tapered lower end of the spinal cord (around L1-L2), marking its termination.
Cervical Enlargement: Thickened area in the cervical region (C4-T1), containing motor neurons for upper limb control.
Lumbar Enlargement: Thickened area in the lumbar region (T11-L1), containing motor neurons for lower limb control.
Cauda Equina: Bundle of spinal nerves and roots extending from the conus medullaris.
Sensory Neurons: Cell bodies in dorsal root ganglia; axons enter the dorsal horn of gray matter.
Interneurons: Found within the spinal cord's gray matter, processing sensory and motor information (dorsal and ventral horns).
Somatic Motor Neurons: Located in the ventral horn, controlling voluntary muscles.
Visceral Motor Neurons (Autonomic): Located in the lateral horn (thoracic and lumbar segments), controlling involuntary muscles and glands.
Dorsal Column-Medial Lemniscal Pathway: Carries fine touch, proprioception, and vibration sensations, crossing over in the medulla.
Spinothalamic Pathway: Carries pain and temperature sensations, crossing over in the spinal cord.
Corticospinal Pathway: Carries voluntary motor commands from the brain, crossing over in the medulla (lateral corticospinal) or spinal cord (anterior corticospinal).
Upper Motor Neuron (UMN) Lesion: Damage to motor neurons in the brain or spinal cord before the spinal cord synapse; results in spasticity, hyperreflexia, and weakness.
Lower Motor Neuron (LMN) Lesion: Damage to motor neurons directly innervating muscles; results in flaccid paralysis, muscle atrophy, and hyporeflexia.
Damage to Dorsal Horn: Results in sensory loss (pain, temperature, proprioception).
Damage to Dorsal Root: Causes sensory loss or numbness.
Damage to Ventral Horn/Root: Results in motor deficits (weakness or paralysis).
Damage to Corticospinal Tract (UMN): Results in spastic paralysis and hyperreflexia.

Peripheral Nervous System (PNS)

Interoceptors: Detect internal stimuli (e.g., stretch receptors in digestive organs).
Exteroceptors: Detect external stimuli (e.g., touch, temperature, vision).
Thermoreceptors: Respond to temperature changes.
Mechanoreceptors: Respond to mechanical pressure or deformation (e.g., Pacinian corpuscles, Merkel discs).
Nociceptors: Detect pain (mechanical, thermal, chemical).
Knee-Jerk (Patellar Reflex): Monosynaptic reflex; maintains posture by stretching quadriceps muscle.
Crossed Extensor Reflex: Reflex that occurs with a withdrawal reflex; supports body weight on opposite limb during withdrawal.
Withdrawal Reflex: Protective reflex removing a body part from a harmful stimulus.
Spinal Reflex Arc: Stimulus → Receptor → Sensory Neuron → Integration Center (spinal cord) → Motor Neuron → Effector (muscle/gland).
Perceptual Processing: Thalamus relays sensory information to the primary sensory cortex for processing.
Stimulus Strength Communication (Frequency Code): Strength of a stimulus is communicated by frequency of action potentials. Stronger stimulus = higher frequency.
Receptor Ending Types:
- Nociceptors: Pain receptors.
- Pacinian/Lamellar Corpuscles: Detect vibration and pressure.

Autonomic Nervous System (ANS)

Sympathetic Nervous System (SNS): Prepares body for "fight or flight"; short preganglionic, long postganglionic neurons; neurotransmitter: norepinephrine (NE).
Parasympathetic Nervous System (PNS): Promotes "rest and digest"; long preganglionic, short postganglionic neurons; neurotransmitter: acetylcholine (ACh).
Sympathetic Functions: Dilated pupils, increased heart rate, bronchodilation, vasoconstriction (except in skeletal muscles), inhibited digestion, etc.
Parasympathetic Functions: Constricted pupils, slowed heart rate, promoted digestion, constricted airways, etc.
Neurotransmitters:
- Acetylcholine (ACh): Released by all preganglionic neurons & PNS postganglionic neurons.
- Norepinephrine (NE): Released by most SNS postganglionic neurons.
Receptor Types:
- Cholinergic receptors (ACh): Nicotinic (postganglionic neurons), muscarinic (target organs in PNS).
- Adrenergic receptors (NE): Alpha (e.g., alpha-1 for vasoconstriction), beta (e.g., beta-1 for heart rate, beta-2 for bronchodilation).
Tables 14.3 & 14.4: Crucial for understanding neurotransmitters, receptors, and their effects, as well as drug interactions.

Special Senses

Eye Anatomy:
- Fovea Centralis: Central retina for sharp central vision.
- Retina: Contains photoreceptors (rods for low-light, cones for color).
- Humors: Aqueous (front) and vitreous (behind) humor maintain shape and refract light.
- Optic Disc: "Blind spot" where optic nerve exits the eye.
Ear Anatomy:
- Tympanic Membrane (eardrum): Vibrates in response to sound waves.
- Otoliths: Small crystals that detect head position (vestibular system).
- Semicircular Canals: Detect rotational head movement.
- Pharyngotympanic Tube (Eustachian tube): Equalizes pressure between middle ear and exterior.
Special Senses Characteristics:
- Photoreceptors (eye): Rods and cones detect different light.
- Taste (gustatory): Taste cells respond to food chemicals.
- Olfaction (smell): Chemoreceptors in nose detect odor molecules.

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Description

This quiz covers key concepts related to the spinal cord's structure and function, including the conus medullaris, cervical and lumbar enlargements, and the types of neurons present. Test your understanding of the sensory and motor pathways and their roles in the central nervous system.