Part 3 Sensory function of the nervous System
Part 3 Sensory Function of the Nervous System
Sensory pathways o Sensory systems allow us to detect, analyze and respond to our environment ascending pathways o Carry information from sensory receptors to the brain o Conscious reach cerebral cortex o Unconscious do not reach cerebral cortex o Sensations from body reach the opposite side of the brain
I Sensory pathways ⚫ Sensory systems allow us to detect, analyze and respond to our environment ⚫ “ascending pathways” ⚫ Carry information from sensory receptors to the brain ⚫ Conscious: reach cerebral cortex ⚫ Unconscious: do not reach cerebral cortex ⚫ Sensations from body reach the opposite side of the brain
1. Sensory receptors A: Free nerve endings(pain, temperature) 060 A B: Pacinian corpuscle(pressure) C: Meissner's corpuscle(touch) B C D: Muscle spindle(stretch)
1. Sensory receptors A: Free nerve endings (pain, temperature) B: Pacinian corpuscle (pressure) C: Meissner’s corpuscle (touch) D: Muscle spindle (stretch) A B C D
Hairy skin Glabrous skin Merkels disk Epidermis Epidermal dermal border Free nerve ending Dermis Meissner corpuscle Hair follicle receptor Pacinian corpuscle Ruffini's ending Ruffini's endings respond to tension and stretch in the skin
Ruffini's endings respond to tension and stretch in the skin
2. Sensory pathways: 3 neurons o 1st: enters spinal cord from periphery o 2nd: crosses over(decussates ), ascends in spinal cord to thalamus o 3rd: projects to somatosensory cortex
2. Sensory pathways: 3 neurons ⚫ 1 st: enters spinal cord from periphery ⚫ 2 nd: crosses over (decussates), ascends in spinal cord to thalamus ⚫ 3 rd: projects to somatosensory cortex
2. 1 Spinothalamic pathway o Carries pain, temperature C touch and pressure signals 1 st neuron enters spinal cord through dorsal root 2nd neuron crosses over in spinal cord, ascends tO thalamus o 3rd neuron projects from thalamus to somatosensory cortex
2.1 Spinothalamic pathway ⚫ Carries pain, temperature, touch and pressure signals ⚫ 1 st neuron enters spinal cord through dorsal root ⚫ 2 nd neuron crosses over in spinal cord; ascends to thalamus ⚫ 3 rd neuron projects from thalamus to somatosensory cortex
Thalami Face Arm spinothalamic pathway Lee
spinothalamic pathway
Spinothalamic Pathway Primary somatosensory cortex (S1) Thalamus Medulla Small dorsal Dorsal Small sensory fil oot axons Spinothalamic tract Painl temperature some touch Spinal cord
Spinothalamic Pathway Small sensory fibres: Pain, temperature, some touch Primary somatosensory cortex (S1) Thalamus Medulla Spinal cord Spinothalamic tract
Spinothalamic damage Left spinothalamic pathway spinal cord injury L3 Loss of sense of Touch .Pain Warmth/cold n rignt leg
Spinothalamic damage spinothalamic pathway Left spinal cord injury Loss of sense of: •Touch •Pain •Warmth/cold in right leg
2.2 Dorsal column pathway o Carries fine touch. vibration and conscious proprioception signals o 1st neuron enters spinal cord through dorsal root ascends to medulla(brain stem) neuron crosses over in C medulla: ascends to thalamus δ处 ●3 neuron projects to 分z somatosensory cortex
2.2 Dorsal column pathway ⚫ Carries fine touch, vibration and conscious proprioception signals ⚫ 1 st neuron enters spinal cord through dorsal root; ascends to medulla (brain stem) ⚫ 2 nd neuron crosses over in medulla; ascends to thalamus ⚫ 3 rd neuron projects to somatosensory cortex